labsim: add IPv6 BGP config layer for the Gateway-API public-v6 rehearsal

The sim's eBGP was IPv4-only; extend it to the v6 family so labsim can rehearse
Cilium BGP advertising a public-style v6 LoadBalancer /64 to the VyOS pair before
it touches production (approved plan: public IPv6 via Cilium BGP + Gateway API).

- sim-net-config.py: bgp6 inside bgp() -- ipv6-unicast peer-group K8S6 over
  fd00:2::11/12/13, prefix-list6 (le 128, /128 host routes), K8S-IN6/OUT6 route-maps
  (export deny -- never hand the cluster a default). ULA fd61:1e00::/64 as the sim
  LB range so nothing leaks into the real HE /48. All v6 lines pass the
  sim-net-apply.sh whitelist.
- sim-ha-config.py: VLANS6 = {2: fd00:2/64} -> routers hold fd00:2::252/253 on
  bond0.2 so they can peer the nodes over v6 (no v6 VRRP VIP; BGP peers the per-box
  address, as production).
- k8s-up.sh: nodes get fd00:2::11/12/13 + dual-stack k3s (dual node-ip, dual
  cluster/service CIDR). Peers line up with sim-net-config K8S_NODES_V6.

Config-gen verified for all three. Live chunk (Cilium v6+BGP+Gateway install,
bring-up, datapath/#26847 proof) is next.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DMVzWZgiKW2wquf5z8S1yH

.gitignore

@@ -31,3 +31,9 @@ node_modules/
 # Asahi build artifacts (large)
 bastion/.asahi-cache/
 bastion/asahi-repo/*.zip
+
+# Regenerated by labsim/dualstack-lab.sh; derived state, not source.
+labsim/dualstack-evidence/
+
+# Runtime snapshots from labsim/cilium-ipam-switch.sh
+labsim/.ipam-switch-state/

bastion/src/bastion/src/templates/install.ks.ts

@@ -134,7 +134,13 @@ lang ${locale}
 keyboard uk
 timezone ${timezone} --utc
 
-network --bootproto=dhcp --activate --hostname=${fqdn}
+# --ipv6=auto, not =dhcp: "auto" follows the router advertisement, so the RA's
+# managed-flag is what steers the node to DHCPv6, and a VLAN with no DHCPv6 yet
+# still installs instead of blocking on a lease that will never come. Failing an
+# OS install because IPv6 was not ready would be a worse trade than a node that
+# briefly has no v6. The address itself comes from a kea DHCPv6 reservation
+# keyed on MAC -- the same source of truth as the v4 address.
+network --bootproto=dhcp --ipv6=auto --activate --hostname=${fqdn}
 
 ${auth}
 ${userDirective}
@@ -366,6 +372,21 @@ fs.inotify.max_user_watches         = 1048576
 SYSCTL
 sysctl --system || true
 
+# -- IPv6 link-local address generation: EUI-64, fleet-wide --
+# A cluster node takes its IPv6 from a MAC-keyed DHCPv6 reservation. kea can only
+# match that reservation when it can recover the node's MAC, and for a modern
+# client that sends a DUID-UUID (no MAC in it) the only place kea can find one is
+# an EUI-64 link-local. NetworkManager's default is stable-privacy (RFC 7217),
+# whose link-local hides the MAC -- so a node on the default silently never gets
+# its reserved address, and with a reservations-only subnet it gets nothing at
+# all. Proven on 2026-09-06: worker0/worker2 (eui64) bound; worker1/spark
+# (default) did not, until flipped. Setting it here means a new node is correct
+# from first boot, before its connection is ever activated.
+cat > /etc/NetworkManager/conf.d/10-ipv6-eui64.conf << 'NMEUI64'
+[connection]
+ipv6.addr-gen-mode=eui64
+NMEUI64
+
 # -- Disable firewalld permanently (k3s/Cilium manage iptables directly) --
 # Note: no '--now' — systemd is not running in the Anaconda chroot
 systemctl disable firewalld || true

bastion/src/bastion/src/templates/ubuntu-autoinstall.ts

@@ -40,34 +40,39 @@ export function renderUbuntuAutoinstall(params: UbuntuAutoinstallParams): string
   // Build the LVM layout to match Fedora kickstart sizes
   const extraLvs: string[] = [];
   if (hasLonghorn) {
-    extraLvs.push(`        - id: lv-longhorn
-          name: longhorn
-          type: lvm_partition
-          volgroup: vg0
-          size: -1
-        - id: fs-longhorn
-          type: format
-          volume: lv-longhorn
-          fstype: xfs
-        - id: mount-longhorn
-          type: mount
-          device: fs-longhorn
-          path: /var/lib/longhorn`);
+    // 6 spaces for the list item, 8 for its keys -- these are siblings of the
+    // lv-home/lv-srv entries in storage.config, which sit at 6. At 8 the
+    // rendered document is not valid YAML at all ("expected <block end>, but
+    // found '-'"), so an Ubuntu node with the longhorn role could never have
+    // installed. Ubuntu + longhorn is exactly the worker shape.
+    extraLvs.push(`      - id: lv-longhorn
+        name: longhorn
+        type: lvm_partition
+        volgroup: vg0
+        size: -1
+      - id: fs-longhorn
+        type: format
+        volume: lv-longhorn
+        fstype: xfs
+      - id: mount-longhorn
+        type: mount
+        device: fs-longhorn
+        path: /var/lib/longhorn`);
   }
   if (hasRancher) {
-    extraLvs.push(`        - id: lv-rancher
-          name: rancher
-          type: lvm_partition
-          volgroup: vg0
-          size: 20G
-        - id: fs-rancher
-          type: format
-          volume: lv-rancher
-          fstype: xfs
-        - id: mount-rancher
-          type: mount
-          device: fs-rancher
-          path: /var/lib/rancher`);
+    extraLvs.push(`      - id: lv-rancher
+        name: rancher
+        type: lvm_partition
+        volgroup: vg0
+        size: 20G
+      - id: fs-rancher
+        type: format
+        volume: lv-rancher
+        fstype: xfs
+      - id: mount-rancher
+        type: mount
+        device: fs-rancher
+        path: /var/lib/rancher`);
   }
 
   const extraLvsBlock = extraLvs.length > 0 ? "\n" + extraLvs.join("\n") : "";
@@ -81,6 +86,11 @@ export function renderUbuntuAutoinstall(params: UbuntuAutoinstallParams): string
     `curtin in-target -- bash -c 'cat > /etc/modules-load.d/k3s.conf << EOF\nbr_netfilter\noverlay\nip_conntrack\nEOF'`,
     // Sysctl for k3s networking
     `curtin in-target -- bash -c 'cat > /etc/sysctl.d/90-k3s.conf << EOF\nnet.bridge.bridge-nf-call-iptables  = 1\nnet.bridge.bridge-nf-call-ip6tables = 1\nnet.ipv4.ip_forward                 = 1\nnet.ipv6.conf.all.forwarding        = 1\nfs.inotify.max_user_instances       = 524288\nfs.inotify.max_user_watches         = 1048576\nEOF'`,
+    // IPv6 link-local = EUI-64, so a MAC-keyed DHCPv6 reservation can match: kea
+    // recovers the node's MAC from an EUI-64 link-local when the client sends a
+    // DUID-UUID (no MAC in it). NM's stable-privacy default hides the MAC and the
+    // node silently never gets its reserved address. Proven 2026-09-06.
+    `curtin in-target -- bash -c 'cat > /etc/NetworkManager/conf.d/10-ipv6-eui64.conf << EOF\n[connection]\nipv6.addr-gen-mode=eui64\nEOF'`,
     // Disable ufw firewall
     `curtin in-target -- systemctl disable ufw || true`,
     // Enable chrony/ntp
@@ -121,7 +131,20 @@ export function renderUbuntuAutoinstall(params: UbuntuAutoinstallParams): string
     `curtin in-target -- bash -c 'IP_ADDR=$(ip -4 addr show | awk "/inet / && !/127.0.0/ {split(\\$2,a,\\"/\\"); print a[1]; exit}"); curl -sf -X POST "http://${serverIp}:${httpPort}/api/progress" -H "Content-Type: application/json" -d "{\\"mac\\":\\"$(ip link show | awk "/ether/ && !/00:00:00:00/ {print \\$2; exit}")\\",\\"stage\\":\\"complete\\",\\"detail\\":\\"ready at $IP_ADDR\\"}" || true'`,
   );
 
-  const lateCommandsYaml = lateCommands.map((c) => `        - "${c}"`).join("\n");
+  // JSON.stringify, not `"${c}"`. JSON is a subset of YAML, so this produces a
+  // correctly escaped double-quoted scalar for free -- and the naive version
+  // was broken in two ways at once, for every role:
+  //
+  //   * embedded double quotes ended the scalar early
+  //     (`echo "tmpfs /tmp ..." >> /etc/fstab` -> "expected <block end>")
+  //   * the heredocs contain REAL newlines, and YAML folds newlines inside a
+  //     double-quoted scalar into spaces -- so even where it parsed, the
+  //     heredoc arrived at the target as one long line and wrote a file with
+  //     no line breaks.
+  //
+  // JSON escaping turns the newlines into \n, which YAML unescapes back to
+  // real newlines on parse, so the heredoc survives intact.
+  const lateCommandsYaml = lateCommands.map((c) => `        - ${JSON.stringify(c)}`).join("\n");
 
   return `#cloud-config
 autoinstall:
@@ -139,6 +162,30 @@ autoinstall:
     allow-pw: false
     authorized-keys:
 ${sshKeysYaml}
+  # Both address families. Without dhcp6 the installer's default is IPv4-only,
+  # so a node provisioned into a dual-stack cluster comes up with no IPv6, k3s
+  # has no v6 node-ip to bind, and it joins as an IPv4-only member of a
+  # dual-stack cluster -- which surfaces later as pods on that node being
+  # unreachable over v6 while the node itself reads Ready.
+  #
+  # The address itself comes from a kea DHCPv6 reservation keyed on MAC, the
+  # same source of truth as the v4 address, so nothing here needs to know it.
+  #
+  # optional: true matters -- it lets the install proceed if the v6 lease is
+  # slow or the VLAN has no DHCPv6 yet, rather than blocking on a timeout. The
+  # node still needs the address before k3s starts, but that is a later step's
+  # problem and failing the OS install over it would be worse.
+  # (No backticks in this comment: it lives inside a TS template literal, and a
+  # backtick here ends the literal and breaks the build.)
+  network:
+    version: 2
+    ethernets:
+      primary:
+        match:
+          name: "en*"
+        dhcp4: true
+        dhcp6: true
+        optional: true
   storage:
     config:
       - id: disk0

bastion/src/bastion/src/templates/vyos-config-spec.ts

@@ -52,6 +52,134 @@ function normalizeDiskPath(value: string | undefined): string {
   return raw.startsWith("/dev/") ? raw : `/dev/${raw}`;
 }
 
+/** Sentinel marking a value that lives in Pulumi config, not in the bundle. */
+const SECRET_PREFIX = "@secret:";
+
+/**
+ * Enable the VyOS HTTP API so the router is manageable the moment it boots.
+ *
+ * This belongs at install time rather than in the Pulumi model: the model is
+ * applied THROUGH this API, so a router that lacks it cannot be brought under
+ * management without a hand-run change on a live firewall. It is also why the
+ * model excludes `service https` outright -- a provider able to rewrite its own
+ * transport can lock itself out permanently.
+ *
+ * `listen-address` is always set. Leaving it unbound would expose a
+ * config-write endpoint on every segment the router touches, the WAN included.
+ */
+function apiSets(apiKey: string, listenAddress: string): VyosSetOp[] {
+  const sets: VyosSetOp[] = [
+    { path: ["service", "https", "api", "keys", "id", "pulumi", "key"], value: apiKey },
+    { path: ["service", "https", "api", "rest"] },
+  ];
+  if (listenAddress !== "") {
+    sets.push({ path: ["service", "https", "listen-address"], value: listenAddress });
+  }
+  return sets;
+}
+
+/** Tag nodes introduced by the API config, needed by the installer's ConfigTree. */
+const API_TAGS: string[][] = [["service", "https", "api", "keys", "id"]];
+
+/**
+ * The address to bind the API to: an explicit choice, else the management
+ * address with its prefix length stripped. Under DHCP there is no address to
+ * bind at build time, so the caller must pass one or the listener stays unbound
+ * and the API is not enabled at all.
+ */
+function apiListenAddress(spec: VyosInstallSpec, mgmtAddress: string): string {
+  if (spec.apiListenAddress !== undefined && spec.apiListenAddress !== "") {
+    return spec.apiListenAddress;
+  }
+  return mgmtAddress.includes("/") ? (mgmtAddress.split("/")[0] ?? "") : "";
+}
+
+/**
+ * Use a Pulumi-rendered bundle as the router's config verbatim.
+ *
+ * Secret-valued nodes are dropped rather than installed with their sentinel
+ * text: writing `@secret:pppoePassword` into config.boot would look configured
+ * while being wrong, which is worse than being absent. The router comes up
+ * without those values and the first `pulumi up` fills them in.
+ *
+ * `system host-name` is forced to the hostname the install was asked for. The
+ * bundle carries the name of whichever router it was exported from, and
+ * installing vyos001's hostname onto vyos002 would collide on the network.
+ */
+function buildFromBundle(
+  params: { hostname: string; defaultPassword: string; disk?: string | undefined },
+  spec: VyosInstallSpec,
+  bundle: NonNullable<VyosInstallSpec["bundle"]>,
+  mgmtAddress: string,
+): VyosConfigSpec {
+  const sets: VyosSetOp[] = [];
+  const dropped: string[] = [];
+  for (const op of bundle.sets) {
+    if (op.value !== undefined && op.value.startsWith(SECRET_PREFIX)) {
+      dropped.push(op.path.join(" "));
+      continue;
+    }
+    if (op.path.length === 2 && op.path[0] === "system" && op.path[1] === "host-name") {
+      continue;
+    }
+    sets.push({
+      path: op.path,
+      ...(op.value === undefined ? {} : { value: op.value }),
+      ...(op.replace === undefined ? {} : { replace: op.replace }),
+    });
+  }
+  sets.unshift({ path: ["system", "host-name"], value: params.hostname });
+
+  if (dropped.length > 0) {
+    console.warn(
+      `vyos ${params.hostname}: ${dropped.length} secret-valued node(s) left unset by the ` +
+        `bundle; run \`pulumi up\` to supply them: ${dropped.join(", ")}`,
+    );
+  }
+
+  const tags = [...bundle.tags];
+  const api = enableApi(spec, params.hostname, mgmtAddress);
+  if (api.length > 0) {
+    sets.push(...api);
+    tags.push(...API_TAGS);
+  }
+
+  return {
+    hostname: params.hostname,
+    imageName: "",
+    password: spec.password ?? params.defaultPassword,
+    console: "K",
+    disk: normalizeDiskPath(params.disk),
+    reportAddress: mgmtAddress.includes("/") ? (mgmtAddress.split("/")[0] ?? "") : "",
+    raid: false,
+    freshConfig: spec.freshConfig ?? false,
+    sets,
+    tags,
+  };
+}
+
+/**
+ * The API config for this install, or nothing when it cannot be enabled safely.
+ *
+ * Refusing to enable it unbound is deliberate. Under DHCP there is no address
+ * known at build time, and the alternative -- binding to every interface --
+ * would publish a config-write endpoint on the WAN. Better to leave the router
+ * SSH-only and say so than to open it everywhere.
+ */
+function enableApi(spec: VyosInstallSpec, hostname: string, mgmtAddress: string): VyosSetOp[] {
+  if (spec.apiKey === undefined || spec.apiKey === "") return [];
+  const listen = apiListenAddress(spec, mgmtAddress);
+  if (listen === "") {
+    console.warn(
+      `vyos ${hostname}: --vyos-api-key given but no address to bind to ` +
+        `(management is "${mgmtAddress}"). Pass --vyos-api-listen <addr>; the HTTP API ` +
+        `has NOT been enabled, so Pulumi cannot manage this router yet.`,
+    );
+    return [];
+  }
+  return apiSets(spec.apiKey, listen);
+}
+
 export function buildVyosConfigSpec(params: {
   hostname: string;
   spec?: VyosInstallSpec | undefined;
@@ -62,6 +190,14 @@ export function buildVyosConfigSpec(params: {
   const spec = params.spec ?? {};
   const mgmt = spec.mgmtInterface ?? "eth0";
   const mgmtAddress = spec.mgmtAddress ?? "dhcp";
+
+  // A rendered bundle replaces the derived config entirely. Deriving a second
+  // opinion alongside it is the drift the bundle exists to prevent: Pulumi and
+  // labctl would each believe they knew the router's config, and the box would
+  // end up with whichever ran last.
+  if (spec.bundle !== undefined) {
+    return buildFromBundle(params, spec, spec.bundle, mgmtAddress);
+  }
   const bondMembers = spec.bondMembers ?? [];
   const vlans = spec.vlans ?? [];
 
@@ -192,6 +328,14 @@ export function buildVyosConfigSpec(params: {
     });
   }
 
+  // Enabled here too, not just for bundle installs: every VyOS this bastion
+  // provisions should be manageable from first boot.
+  const api = enableApi(spec, params.hostname, mgmtAddress);
+  if (api.length > 0) {
+    sets.push(...api);
+    tags.push(...API_TAGS);
+  }
+
   return {
     hostname: params.hostname,
     imageName: "",

bastion/src/bastion/tests/ubuntu-autoinstall.test.ts

@@ -0,0 +1,87 @@
+// The Ubuntu autoinstall document must be valid YAML for EVERY role.
+//
+// There was no test here, and the template shipped a document that did not
+// parse: the longhorn/rancher LVM entries were indented 8 spaces while their
+// siblings in storage.config sit at 6, giving "expected <block end>, but found
+// '-'". Every role that gets a longhorn volume -- which is the worker shape --
+// rendered an uninstallable document. A `toContain` assertion would not have
+// caught that; only parsing does.
+//
+// Parsed with python3's yaml rather than a new npm dependency, mirroring how
+// kickstart.test.ts shells out to `ksvalidator`: the point is to check the
+// artefact with a real parser, not to grow the dependency tree.
+
+import { describe, it, expect } from "vitest";
+import { execFileSync } from "node:child_process";
+import { writeFileSync, unlinkSync } from "node:fs";
+import { renderUbuntuAutoinstall } from "../src/templates/ubuntu-autoinstall.js";
+
+const base = {
+  hostname: "n6",
+  disk: "/dev/sda",
+  domain: "ad.itaz.eu",
+  ubuntuVersion: "24.04",
+  timezone: "Europe/London",
+  locale: "en_GB.UTF-8",
+  serverIp: "10.0.0.1",
+  httpPort: 8080,
+  sshKeys: ["ssh-ed25519 AAAAtest test@lab"],
+  adminUser: "root",
+};
+
+/** Parse with python3's yaml and return the document as JSON. */
+function parseYaml(text: string, label: string): Record<string, any> {
+  const tmp = `/tmp/autoinstall-test-${label}.yaml`;
+  writeFileSync(tmp, text);
+  try {
+    const out = execFileSync(
+      "python3",
+      ["-c", "import sys,yaml,json; json.dump(yaml.safe_load(open(sys.argv[1])), sys.stdout)", tmp],
+      { encoding: "utf-8" },
+    );
+    return JSON.parse(out);
+  } catch (err: unknown) {
+    const msg = err instanceof Error ? (err as { stderr?: string }).stderr ?? err.message : String(err);
+    throw new Error(`autoinstall YAML did not parse for ${label}: ${msg}`);
+  } finally {
+    try { unlinkSync(tmp); } catch { /* ignore */ }
+  }
+}
+
+describe("renderUbuntuAutoinstall", () => {
+  for (const role of ["vanilla", "worker", "infra"]) {
+    it(`renders parseable YAML for role=${role}`, () => {
+      const doc = parseYaml(renderUbuntuAutoinstall({ ...base, role }), role);
+      expect(doc.autoinstall).toBeDefined();
+      expect(doc.autoinstall.version).toBe(1);
+      // storage.config must be a flat list; the indentation bug produced a
+      // nested map here, which is how it went unnoticed.
+      expect(Array.isArray(doc.autoinstall.storage.config)).toBe(true);
+    });
+  }
+
+  it("gives the longhorn role its volume as a sibling entry, not a nested map", () => {
+    const doc = parseYaml(renderUbuntuAutoinstall({ ...base, role: "worker" }), "longhorn");
+    const ids = doc.autoinstall.storage.config.map((e: { id: string }) => e.id);
+    expect(ids).toContain("lv-longhorn");
+    expect(ids).toContain("mount-longhorn");
+  });
+
+  it("sets EUI-64 link-local so MAC-keyed DHCPv6 reservations can match", () => {
+    const doc = parseYaml(renderUbuntuAutoinstall({ ...base, role: "worker" }), "eui64");
+    const late = (doc.autoinstall["late-commands"] as string[]).join("\n");
+    expect(late).toContain("10-ipv6-eui64.conf");
+    expect(late).toContain("ipv6.addr-gen-mode=eui64");
+  });
+
+  it("requests both address families on the primary NIC", () => {
+    const doc = parseYaml(renderUbuntuAutoinstall({ ...base, role: "worker" }), "net");
+    const eth = doc.autoinstall.network.ethernets.primary;
+    expect(eth.dhcp4).toBe(true);
+    // Without this a node provisioned into a dual-stack cluster comes up with
+    // no IPv6 and joins as an IPv4-only member.
+    expect(eth.dhcp6).toBe(true);
+    // The install must not block waiting for a v6 lease that may never come.
+    expect(eth.optional).toBe(true);
+  });
+});

bastion/src/bastion/tests/vyos-bundle.test.ts

@@ -0,0 +1,155 @@
+import { describe, it, expect, vi } from "vitest";
+import type { VyosBundle } from "@lab/shared";
+import { buildVyosConfigSpec } from "../src/templates/vyos-config-spec.js";
+
+/**
+ * A bundle is what makes "one config, two apply paths" true rather than
+ * aspirational: `pulumi up` POSTs the subtree model to a running router, labctl
+ * writes the same model into config.boot during a PXE install. These tests pin
+ * the properties that keep the two honest.
+ */
+const bundle: VyosBundle = {
+  sets: [
+    { path: ["system", "host-name"], value: "vyos001" },
+    { path: ["interfaces", "bonding", "bond0", "address"], value: "192.168.1.252/24" },
+    { path: ["interfaces", "bonding", "bond0", "member", "interface"], value: "eth1", replace: false },
+    { path: ["interfaces", "bonding", "bond0", "vif", "53", "disable"] },
+    { path: ["interfaces", "pppoe", "pppoe0", "authentication", "password"], value: "@secret:pppoePassword" },
+    { path: ["interfaces", "pppoe", "pppoe0", "mtu"], value: "1492" },
+  ],
+  tags: [["interfaces", "bonding", "bond0"], ["interfaces", "ethernet"]],
+};
+
+const build = (hostname: string, extra: Record<string, unknown> = {}) =>
+  buildVyosConfigSpec({
+    hostname,
+    spec: { bundle, ...extra },
+    defaultPassword: "changeme",
+  });
+
+describe("vyos config spec from a Pulumi bundle", () => {
+  it("applies non-secret nodes verbatim, preserving valuelessness and replace:false", () => {
+    const spec = build("vyos001");
+
+    expect(spec.sets).toContainEqual({
+      path: ["interfaces", "bonding", "bond0", "address"],
+      value: "192.168.1.252/24",
+    });
+    // A multi-value node must keep replace:false or the second bond member
+    // overwrites the first.
+    expect(spec.sets).toContainEqual({
+      path: ["interfaces", "bonding", "bond0", "member", "interface"],
+      value: "eth1",
+      replace: false,
+    });
+    // A valueless node must not acquire a value on the way through.
+    expect(spec.sets).toContainEqual({
+      path: ["interfaces", "bonding", "bond0", "vif", "53", "disable"],
+    });
+    expect(spec.tags).toEqual(bundle.tags);
+  });
+
+  it("drops secret-valued nodes instead of installing the sentinel text", () => {
+    const warn = vi.spyOn(console, "warn").mockImplementation(() => {});
+    const spec = build("vyos001");
+
+    const values = spec.sets.map((s) => s.value ?? "");
+    expect(values.some((v) => v.startsWith("@secret:"))).toBe(false);
+    expect(spec.sets.some((s) => s.path.includes("authentication"))).toBe(false);
+    // Silently dropping the WAN credential would leave someone debugging a dead
+    // PPPoE link, so it has to be said out loud.
+    expect(warn).toHaveBeenCalledWith(expect.stringContaining("pulumi up"));
+    warn.mockRestore();
+  });
+
+  it("forces the hostname the install was asked for, not the bundle's", () => {
+    // The bundle is exported from one router and reused for its peer; taking the
+    // hostname from it would put two vyos001s on the network.
+    const spec = build("vyos002");
+    const hostnames = spec.sets.filter(
+      (s) => s.path.length === 2 && s.path[0] === "system" && s.path[1] === "host-name",
+    );
+    expect(hostnames).toEqual([{ path: ["system", "host-name"], value: "vyos002" }]);
+  });
+
+  it("still honours installer inputs, which are not router config", () => {
+    const spec = buildVyosConfigSpec({
+      hostname: "vyos001",
+      spec: { bundle, password: "s3cret", freshConfig: true },
+      defaultPassword: "changeme",
+      disk: "nvme0n1",
+    });
+    expect(spec.password).toBe("s3cret");
+    expect(spec.freshConfig).toBe(true);
+    expect(spec.disk).toBe("/dev/nvme0n1");
+  });
+
+  it("enables the HTTP API at install so Pulumi can manage the router from first boot", () => {
+    const warn = vi.spyOn(console, "warn").mockImplementation(() => {});
+    const spec = buildVyosConfigSpec({
+      hostname: "vyos001",
+      spec: { bundle, apiKey: "k3y", apiListenAddress: "10.0.1.252" },
+      defaultPassword: "changeme",
+    });
+
+    expect(spec.sets).toContainEqual({
+      path: ["service", "https", "api", "keys", "id", "pulumi", "key"],
+      value: "k3y",
+    });
+    expect(spec.sets).toContainEqual({ path: ["service", "https", "api", "rest"] });
+    expect(spec.sets).toContainEqual({
+      path: ["service", "https", "listen-address"],
+      value: "10.0.1.252",
+    });
+    // The key id is a tag node; without this the installer's ConfigTree rejects it.
+    expect(spec.tags).toContainEqual(["service", "https", "api", "keys", "id"]);
+    warn.mockRestore();
+  });
+
+  it("binds the API to the static management address when none is given", () => {
+    const spec = buildVyosConfigSpec({
+      hostname: "vyos001",
+      spec: { apiKey: "k3y", mgmtAddress: "192.168.1.252/24" },
+      defaultPassword: "changeme",
+    });
+    expect(spec.sets).toContainEqual({
+      path: ["service", "https", "listen-address"],
+      value: "192.168.1.252",
+    });
+  });
+
+  it("refuses to enable the API unbound rather than exposing it on the WAN", () => {
+    const warn = vi.spyOn(console, "warn").mockImplementation(() => {});
+    // Management is DHCP, so there is no address to bind at build time. Binding
+    // to everything would put a config-write endpoint on the WAN.
+    const spec = buildVyosConfigSpec({
+      hostname: "vyos001",
+      spec: { apiKey: "k3y", mgmtAddress: "dhcp" },
+      defaultPassword: "changeme",
+    });
+    expect(spec.sets.some((s) => s.path[0] === "service" && s.path[1] === "https")).toBe(false);
+    expect(warn).toHaveBeenCalledWith(expect.stringContaining("has NOT been enabled"));
+    warn.mockRestore();
+  });
+
+  it("does not enable the API when no key is supplied", () => {
+    const spec = buildVyosConfigSpec({
+      hostname: "vyos001",
+      spec: { mgmtAddress: "192.168.1.252/24" },
+      defaultPassword: "changeme",
+    });
+    expect(spec.sets.some((s) => s.path[0] === "service" && s.path[1] === "https")).toBe(false);
+  });
+
+  it("ignores the derived path entirely when a bundle is present", () => {
+    // Belt and braces: even if topology flags reach this far (the CLI rejects
+    // them), the bundle must win rather than merge.
+    const spec = buildVyosConfigSpec({
+      hostname: "vyos001",
+      spec: { bundle, bondMembers: ["eth2", "eth3"], vlans: [{ id: 99, address: "10.9.9.1/24" }] },
+      defaultPassword: "changeme",
+    });
+    expect(spec.sets.some((s) => s.path.includes("99"))).toBe(false);
+    expect(spec.sets.filter((s) => s.value === "eth2" || s.value === "eth3")).toEqual([]);
+  });
+});

bastion/src/cli/src/commands/install.ts

@@ -1,11 +1,42 @@
 // CLI command: provision install
 // Queue a discovered machine for OS installation via labd.
 
+import { readFileSync } from "node:fs";
 import { Command, Option, InvalidArgumentError } from "commander";
 import { isValidOsId, SUPPORTED_OS, SUPPORTED_ROLES, ROLE_REGISTRY } from "@lab/shared";
-import type { VyosInstallSpec, VyosVlanSpec } from "@lab/shared";
+import type { VyosBundle, VyosInstallSpec, VyosVlanSpec } from "@lab/shared";
 import { getLabdClient } from "../api/config.js";
 
+/**
+ * Load one router's config out of a Pulumi-rendered bundle.
+ *
+ * The bundle is produced by `kubernetes-deployment` (npm run vyos:bundle) and
+ * holds every router it manages, keyed by name. Selecting by hostname here is
+ * what keeps bring-up and `pulumi up` describing the same box: labctl replays
+ * the declared config rather than deriving its own.
+ */
+export function loadVyosBundle(path: string, hostname: string): VyosBundle {
+  let parsed: { version?: number; routers?: Record<string, VyosBundle> };
+  try {
+    parsed = JSON.parse(readFileSync(path, "utf8"));
+  } catch (e) {
+    throw new InvalidArgumentError(`Cannot read VyOS bundle ${path}: ${(e as Error).message}`);
+  }
+  if (parsed.version !== 1) {
+    throw new InvalidArgumentError(
+      `VyOS bundle ${path} has version ${parsed.version ?? "<none>"}; this labctl understands 1`,
+    );
+  }
+  const router = parsed.routers?.[hostname];
+  if (router === undefined) {
+    const known = Object.keys(parsed.routers ?? {}).join(", ") || "<none>";
+    throw new InvalidArgumentError(
+      `VyOS bundle ${path} has no entry for "${hostname}" (has: ${known})`,
+    );
+  }
+  return router;
+}
+
 /** Parse a repeated --vlan flag: "<id>:<cidr>[:<description>]". */
 export function parseVlan(value: string, previous: VyosVlanSpec[] = []): VyosVlanSpec[] {
   const parts = value.split(":");
@@ -88,6 +119,20 @@ export function registerInstallCommand(parent: Command): void {
     .option("--vyos-password <password>", "VyOS: password for the 'vyos' user")
     .option("--vyos-hwid <iface=mac>", "VyOS: pin an interface name to a MAC via hw-id (repeatable)", parseHwId)
     .option("--vyos-fresh-config", "VyOS: on reinstall, overwrite the preserved config with the generated one")
+    .option(
+      "--vyos-bundle <path>",
+      "VyOS: apply a Pulumi-rendered bundle verbatim (kubernetes-deployment/infra/vyos/vyos-bundle.json). " +
+        "Replaces the derived --vyos-bond/--vlan/... config; secret values are left unset for `pulumi up`.",
+    )
+    .option(
+      "--vyos-api-key <key>",
+      "VyOS: enable the HTTP API with this key so Pulumi can manage the router from first boot",
+    )
+    .option(
+      "--vyos-api-listen <addr>",
+      "VyOS: address the HTTP API binds to (default: the static management address). " +
+        "Required when management is DHCP; the API is never bound to all interfaces.",
+    )
     .action(async (mac: string, hostname: string, opts: {
       role: string;
       os: string;
@@ -104,6 +149,9 @@ export function registerInstallCommand(parent: Command): void {
       vyosPassword?: string;
       vyosHwid?: Record<string, string>;
       vyosFreshConfig?: boolean;
+      vyosBundle?: string;
+      vyosApiKey?: string;
+      vyosApiListen?: string;
     }) => {
       if (!isValidOsId(opts.os)) {
         console.error(`Unknown OS: ${opts.os}. Supported: ${SUPPORTED_OS.join(", ")}`);
@@ -159,9 +207,31 @@ export function registerInstallCommand(parent: Command): void {
         ...(opts.vyosMgmtVlan !== undefined && opts.vyosMgmtVlan !== ""
           ? { mgmtVlan: parseVlan(opts.vyosMgmtVlan)[0] as VyosVlanSpec } : {}),
         ...(opts.vyosFreshConfig === true ? { freshConfig: true } : {}),
+        ...(opts.vyosBundle !== undefined && opts.vyosBundle !== ""
+          ? { bundle: loadVyosBundle(opts.vyosBundle, hostname) } : {}),
+        ...(opts.vyosApiKey !== undefined && opts.vyosApiKey !== ""
+          ? { apiKey: opts.vyosApiKey } : {}),
+        ...(opts.vyosApiListen !== undefined && opts.vyosApiListen !== ""
+          ? { apiListenAddress: opts.vyosApiListen } : {}),
       };
       const hasVyosOptions = Object.keys(vyos).length > 0;
 
+      // A bundle already describes the whole router. Accepting derived topology
+      // flags alongside it would silently discard them (the bundle wins in
+      // buildVyosConfigSpec), so say so rather than appear to honour both.
+      if (vyos.bundle !== undefined) {
+        const derived = ["mgmtInterface", "mgmtAddress", "bondMembers", "bondAddress",
+                         "bondVrrp", "vrrpPriority", "vlans", "mgmtVlan"] as const;
+        const conflicting = derived.filter((k) => vyos[k] !== undefined);
+        if (conflicting.length > 0) {
+          console.error(
+            `--vyos-bundle describes the whole router; these would be ignored: ${conflicting.join(", ")}`,
+          );
+          console.error("Remove them, or change the bundle in kubernetes-deployment and re-render.");
+          process.exit(1);
+        }
+      }
+
       if (hasVyosOptions && !opts.os.startsWith("vyos")) {
         console.error(`VyOS options require --os vyos-rolling (got --os ${opts.os})`);
         process.exit(1);

bastion/src/modules/modules/k3s/bin/render-config.ts

@@ -0,0 +1,42 @@
+#!/usr/bin/env node
+// Render /etc/rancher/k3s/config.yaml using the PRODUCTION generator.
+//
+// Exists so labsim (and anything else) can produce the exact config.yaml a node
+// would get from `labctl install`, without an SSH/OperationContext. Driving the
+// rehearsal through this means the sim tests the same code path production runs
+// -- if generateServerConfig ever changes shape, the sim moves with it.
+//
+// All input via env, so a sim's cloud-init or a shell can call it plainly:
+//
+//   ROLE=infra HOSTNAME=k8s1 IP=172.31.2.11 render-config.ts        # cluster-init server
+//   ROLE=infra HOSTNAME=k8s2 IP=172.31.2.12 \
+//     K3S_SERVER_URL=https://172.31.2.11:6443 K3S_TOKEN=... render-config.ts   # joining server
+//   ROLE=worker HOSTNAME=k8s4 IP=172.31.2.14 K3S_SERVER_URL=... K3S_TOKEN=... render-config.ts  # agent
+//
+// Dual-stack is opt-in and matches K3sConfig exactly: set IPV6, CLUSTER_CIDR,
+// SERVICE_CIDR (comma-separated families) and the generator emits the dual
+// node-ip + CIDRs. Omit them and the output is byte-identical to a v4-only node.
+import { generateServerConfig, generateAgentConfig } from "../src/operations/k3s-config.js";
+import type { K3sConfig } from "../src/types.js";
+import type { Role } from "@lab/shared";
+
+const env = process.env;
+const role = (env.ROLE ?? "worker") as Role;
+const isServer = role === "infra" || role === "labcontroller";
+
+const splitCsv = (v: string | undefined): string[] | undefined =>
+  v ? v.split(",").map((s) => s.trim()).filter(Boolean) : undefined;
+
+const cfg: K3sConfig = {
+  hostname: env.HOSTNAME ?? "node",
+  ip: env.IP ?? (() => { throw new Error("IP is required"); })(),
+  role,
+  k3sServerUrl: env.K3S_SERVER_URL,
+  k3sToken: env.K3S_TOKEN,
+  tlsSans: splitCsv(env.TLS_SANS),
+  ipv6: env.IPV6,
+  clusterCidr: splitCsv(env.CLUSTER_CIDR),
+  serviceCidr: splitCsv(env.SERVICE_CIDR),
+};
+
+process.stdout.write(isServer ? generateServerConfig(cfg) : generateAgentConfig(cfg));

bastion/src/modules/modules/k3s/src/install.ts

@@ -215,7 +215,9 @@ echo "  Using network device: \$DEFAULT_DEV"
 
 KUBECONFIG=/etc/rancher/k3s/k3s.yaml cilium install \\
   --set kubeProxyReplacement=true \\
-  --set ipam.mode=kubernetes \\
+  --set ipam.mode=cluster-pool \\
+  --set ipam.operator.clusterPoolIPv4PodCIDRList='{10.42.0.0/16}' \\
+  --set ipam.operator.clusterPoolIPv4MaskSize=24 \\
   --set devices="\$DEFAULT_DEV" \\
   --set nodePort.directRoutingDevice="\$DEFAULT_DEV"
 

bastion/src/modules/modules/k3s/src/operations/cilium.ts

@@ -47,7 +47,9 @@ export const installCilium: Operation = async (ctx): Promise<OperationResult> =>
   const installResult = await ctx.ssh.exec(
     `KUBECONFIG=/etc/rancher/k3s/k3s.yaml cilium install \
       --set kubeProxyReplacement=true \
-      --set ipam.mode=kubernetes \
+      --set ipam.mode=cluster-pool \
+      --set ipam.operator.clusterPoolIPv4PodCIDRList='{10.42.0.0/16}' \
+      --set ipam.operator.clusterPoolIPv4MaskSize=24 \
       --set k8sServiceHost=127.0.0.1 \
       --set k8sServicePort=6444 \
       --set cni.exclusive=false \

bastion/src/modules/modules/k3s/src/operations/index.ts

@@ -5,7 +5,7 @@ export { growRancherLv } from "./rancher-storage.js";
 export { enableIscsi } from "./iscsi.js";
 export { disableFirewall } from "./firewall.js";
 export { setSelinuxPermissive } from "./selinux.js";
-export { writeK3sConfig } from "./k3s-config.js";
+export { writeK3sConfig, generateServerConfig, generateAgentConfig } from "./k3s-config.js";
 export { writeAuditPolicy } from "./audit-policy.js";
 export { cleanupStaleCni } from "./cni-cleanup.js";
 export { installK3sBinary } from "./k3s-install.js";

bastion/src/modules/modules/k3s/src/operations/k3s-config.ts

@@ -7,8 +7,52 @@ function isServerRole(role: string): boolean {
   return role === "infra" || role === "labcontroller";
 }
 
-function generateServerConfig(config: K3sConfig): string {
-  const tlsSans = [config.hostname, config.ip, ...(config.tlsSans ?? [])];
+/**
+ * The address-family block: `cluster-cidr`, `service-cidr` and `node-ip`.
+ *
+ * Emitted ONLY when the corresponding config is supplied, and that is
+ * deliberate. With no `ipv6` and no CIDRs this returns "", so the generated
+ * file is byte-identical to what every existing node already has -- no diff,
+ * so `writeRemoteFile` reports unchanged and nothing restarts k3s. Dual-stack
+ * is therefore opt-in per node rather than a flag day.
+ *
+ * `node-ip` is only written once there is a second family to name. k3s
+ * auto-detects a sensible IPv4 on its own, and writing it out unconditionally
+ * would rewrite the config of five healthy nodes to tell them what they had
+ * already worked out.
+ */
+function addressFamilyLines(config: K3sConfig, opts: { cidrs: boolean }): string {
+  const lines: string[] = [];
+  if (opts.cidrs && config.clusterCidr?.length) {
+    lines.push(`cluster-cidr: "${config.clusterCidr.join(",")}"`);
+  }
+  if (opts.cidrs && config.serviceCidr?.length) {
+    lines.push(`service-cidr: "${config.serviceCidr.join(",")}"`);
+  }
+  if (config.ipv6) {
+    // Order matters to k3s: the FIRST entry is the primary family, and the
+    // supported single-to-dual-stack conversion is the one that preserves it.
+    // IPv4 stays primary so existing Services keep their ClusterIP.
+    lines.push(`node-ip: "${config.ip},${config.ipv6}"`);
+  }
+  return lines.length ? `${lines.join("\n")}\n` : "";
+}
+
+// Exported so the exact production config.yaml can be rendered outside an SSH
+// context -- notably by the labsim 3-server-etcd rehearsal, which must drive its
+// nodes through THIS generator rather than a parallel set of INSTALL_K3S_EXEC
+// flags, or it proves a mechanism production does not run.
+export function generateServerConfig(config: K3sConfig): string {
+  // The IPv6 address goes in the cert too. Without it, anything that reaches
+  // this apiserver over v6 -- a peer server joining, or kubectl against the v6
+  // address -- fails TLS verification, and the error names the certificate
+  // rather than the missing SAN, which is a long way from the cause.
+  const tlsSans = [
+    config.hostname,
+    config.ip,
+    ...(config.ipv6 ? [config.ipv6] : []),
+    ...(config.tlsSans ?? []),
+  ];
   const isJoining = !!config.k3sServerUrl;
   const clusterLines = isJoining
     ? `server: "${config.k3sServerUrl}"\ntoken: "${config.k3sToken}"`
@@ -21,7 +65,7 @@ function generateServerConfig(config: K3sConfig): string {
   // and never expire.
   return `# k3s server configuration — CIS hardened, etcd HA
 ${clusterLines}
-protect-kernel-defaults: true
+${addressFamilyLines(config, { cidrs: true })}protect-kernel-defaults: true
 secrets-encryption: true
 write-kubeconfig-mode: "0640"
 
@@ -51,8 +95,13 @@ ${tlsSans.map((s) => `  - "${s}"`).join("\n")}
 `;
 }
 
-function generateAgentConfig(): string {
-  return `protect-kernel-defaults: true
+// Takes the config now: an agent needs its own dual `node-ip` just as much as a
+// server does. Without one it joins as an IPv4-only node into a dual-stack
+// cluster, gets no IPv6 pod CIDR, and the failure surfaces later as pods on that
+// node being unreachable over v6 while the node itself reads Ready.
+// It takes no cluster/service CIDRs -- those are server-side only.
+export function generateAgentConfig(config: K3sConfig): string {
+  return `${addressFamilyLines(config, { cidrs: false })}protect-kernel-defaults: true
 node-label:
   - "node-role.kubernetes.io/worker=true"
   - "node.longhorn.io/create-default-disk=config"
@@ -64,11 +113,41 @@ kubelet-arg:
 }
 
 export const writeK3sConfig: Operation = async (ctx): Promise<OperationResult> => {
+  // Refuse to name an address the node does not have.
+  //
+  // Most of this estate is SSH-onboard, not PXE-provisioned: Asahi cannot PXE
+  // at all, and the DGX Sparks run NVIDIA's own OS and must never be
+  // reinstalled. For those nodes the install templates govern nothing and this
+  // module is the ONLY labctl touchpoint, so nothing upstream can guarantee the
+  // vendor OS actually took a DHCPv6 lease.
+  //
+  // Writing node-ip for a missing address does not fail here -- it fails later,
+  // when k3s will not start, with an error about binding rather than about
+  // addressing. Checking costs one ssh round trip and turns a confusing
+  // start-up failure into a sentence naming the address and the node.
+  if (ctx.config.ipv6) {
+    const probe = await ctx.ssh.exec(
+      `ip -6 -o addr show 2>/dev/null | grep -qF " ${ctx.config.ipv6}/" && echo present || true`,
+      sshOpts(ctx),
+    );
+    if (!probe.stdout.includes("present")) {
+      return {
+        success: false,
+        changed: false,
+        message: `Node does not have IPv6 ${ctx.config.ipv6}`,
+        error:
+          `k3s config would set node-ip to ${ctx.config.ipv6}, but that address is not on any ` +
+          `interface. k3s resolves node-ip at start-up and would fail to bind. Check the node ` +
+          `took its DHCPv6 lease (a kea reservation keyed on its MAC) before retrying.`,
+      };
+    }
+  }
+
   await ctx.ssh.exec("mkdir -p /etc/rancher/k3s", sshOpts(ctx));
 
   const content = isServerRole(ctx.config.role)
     ? generateServerConfig(ctx.config)
-    : generateAgentConfig();
+    : generateAgentConfig(ctx.config);
 
   const changed = await writeRemoteFile(ctx, "/etc/rancher/k3s/config.yaml", content);
 

bastion/src/modules/modules/k3s/src/types.ts

@@ -16,6 +16,33 @@ export interface K3sConfig {
 
   // Additional TLS SANs for API server certificate
   tlsSans?: string[] | undefined;
+
+  /**
+   * IPv6 address of this node on the cluster VLAN. Its PRESENCE is what makes a
+   * node dual-stack: supply it and `node-ip` is emitted as `<v4>,<v6>`; omit it
+   * and the generated config is byte-identical to the IPv4-only one.
+   *
+   * It must be a real address on the node before k3s starts. k3s resolves
+   * node-ip at boot, so a SLAAC or DHCPv6 lease that has not landed yet leaves
+   * the node with no usable v6 identity. The estate takes it from a kea DHCPv6
+   * reservation keyed on MAC, the same way it takes its IPv4 address.
+   */
+  ipv6?: string | undefined;
+
+  /**
+   * Pod and Service ranges, one entry per address family. Passed rather than
+   * hardcoded so the ranges stay configuration -- and so labsim can rehearse
+   * with its own addresses through this same generator, instead of a parallel
+   * set of INSTALL_K3S_EXEC flags that would prove a different mechanism.
+   *
+   * k3s validates the two together and crash-loops on a mismatch (a dual
+   * cluster-cidr with a single-family service-cidr, say), which is a safe
+   * failure but an avoidable one: set both or neither.
+   *
+   * Servers only -- agents take neither.
+   */
+  clusterCidr?: string[] | undefined;
+  serviceCidr?: string[] | undefined;
 }
 
 /** SSH execution interface injected into operations. */

bastion/src/modules/modules/k3s/tests/operations.test.ts

@@ -268,6 +268,108 @@ describe("writeK3sConfig", () => {
     expect(writeCall).toContain("protect-kernel-defaults: true");
     expect(writeCall).not.toContain("secrets-encryption");
   });
+
+  // --- dual-stack ---
+  //
+  // The property that matters most is the NEGATIVE one: with no ipv6 and no
+  // CIDRs the output must be byte-identical to what the five existing nodes
+  // already have on disk. If it is not, rolling this out rewrites every node's
+  // config.yaml and restarts a healthy cluster to tell it what it already knew.
+
+  // With an ipv6 configured there is an extra ssh round trip up front -- the
+  // probe that checks the address is really on the node -- so the write lands
+  // one call later.
+  const writtenBy = async (config: Parameters<typeof mockCtx>[0]) => {
+    const ctx = mockCtx(config);
+    const hasV6 = !!(config as { ipv6?: string }).ipv6;
+    if (hasV6) ctx.ssh.exec.mockResolvedValueOnce(stdout("present"));
+    ctx.ssh.exec
+      .mockResolvedValueOnce(OK)
+      .mockResolvedValueOnce(stdout("__LABCTL_NOT_FOUND__"))
+      .mockResolvedValueOnce(OK);
+    await writeK3sConfig(ctx);
+    return ctx.ssh.exec.mock.calls[hasV6 ? 3 : 2]![0] as string;
+  };
+
+  it("emits no address-family lines at all when single-stack", async () => {
+    const server = await writtenBy({ hostname: "n1.lab", ip: "10.0.1.1", role: "infra" });
+    expect(server).not.toContain("node-ip");
+    expect(server).not.toContain("cluster-cidr");
+    expect(server).not.toContain("service-cidr");
+
+    const agent = await writtenBy({ role: "worker" });
+    expect(agent).not.toContain("node-ip");
+    // Nothing inserted ahead of, or between, the lines the agent config has
+    // always opened with.
+    expect(agent).toContain("protect-kernel-defaults: true\nnode-label:");
+  });
+
+  it("emits dual node-ip and CIDRs on a server, IPv4 first", async () => {
+    const out = await writtenBy({
+      hostname: "n1.lab",
+      ip: "192.168.8.23",
+      role: "infra",
+      ipv6: "2001:470:187e:2::23",
+      clusterCidr: ["10.42.0.0/16", "2001:470:187e:1000::/56"],
+      serviceCidr: ["10.43.0.0/16", "2001:470:187e:1fff::/112"],
+    });
+    expect(out).toContain('node-ip: "192.168.8.23,2001:470:187e:2::23"');
+    expect(out).toContain('cluster-cidr: "10.42.0.0/16,2001:470:187e:1000::/56"');
+    expect(out).toContain('service-cidr: "10.43.0.0/16,2001:470:187e:1fff::/112"');
+    // IPv4 must stay the primary family -- that is the supported conversion
+    // path and what lets existing Services keep their ClusterIP.
+    expect(out.indexOf("10.42.0.0/16")).toBeLessThan(out.indexOf("2001:470:187e:1000::/56"));
+    // still a valid server config
+    expect(out).toContain("cluster-init: true");
+    expect(out).toContain("secrets-encryption: true");
+    // the v6 address must be a TLS SAN, or a peer joining over v6 fails
+    // verification with an error that names the cert, not the missing SAN
+    expect(out).toContain('  - "2001:470:187e:2::23"');
+  });
+
+  it("gives an AGENT its own dual node-ip but no CIDRs", async () => {
+    const out = await writtenBy({
+      ip: "192.168.8.12",
+      role: "worker",
+      ipv6: "2001:470:187e:2::12",
+      // deliberately supplied: an agent must ignore them
+      clusterCidr: ["10.42.0.0/16", "2001:470:187e:1000::/56"],
+      serviceCidr: ["10.43.0.0/16", "2001:470:187e:1fff::/112"],
+    });
+    expect(out).toContain('node-ip: "192.168.8.12,2001:470:187e:2::12"');
+    expect(out).not.toContain("cluster-cidr");
+    expect(out).not.toContain("service-cidr");
+  });
+
+  it("refuses to write a config naming an IPv6 the node does not have", async () => {
+    // The SSH-onboard case: Asahi and the DGX Sparks run an OS labctl never
+    // installed, so nothing upstream guarantees a DHCPv6 lease was taken.
+    // Writing the config anyway defers the failure to k3s start-up, where it
+    // reads as a bind error rather than a missing address.
+    const ctx = mockCtx({ ip: "192.168.8.12", role: "worker", ipv6: "2001:470:187e:2::12" });
+    ctx.ssh.exec.mockResolvedValueOnce(stdout("")); // probe: address absent
+
+    const result = await writeK3sConfig(ctx);
+    expect(result.success).toBe(false);
+    expect(result.changed).toBe(false);
+    expect(result.error).toContain("2001:470:187e:2::12");
+    // and it must not have written anything
+    expect(ctx.ssh.exec).toHaveBeenCalledTimes(1);
+  });
+
+  it("does not write node-ip for a v4-only node even when CIDRs are given", async () => {
+    // Guards the flag-day risk: supplying ranges alone must not start rewriting
+    // node identity on nodes that have no IPv6 yet.
+    const out = await writtenBy({
+      hostname: "n1.lab",
+      ip: "10.0.1.1",
+      role: "infra",
+      clusterCidr: ["10.42.0.0/16"],
+      serviceCidr: ["10.43.0.0/16"],
+    });
+    expect(out).toContain('cluster-cidr: "10.42.0.0/16"');
+    expect(out).not.toContain("node-ip");
+  });
 });
 
 // --- CNI Cleanup ---

bastion/src/shared/src/index.ts

@@ -10,6 +10,8 @@ export type {
   BastionConfig,
   VyosVlanSpec,
   VyosInstallSpec,
+  VyosBundle,
+  VyosBundleSetOp,
 } from "./types/index.js";
 
 export { SUPPORTED_OS, SUPPORTED_ROLES, ROLE_REGISTRY, isValidOsId } from "./types/index.js";

bastion/src/shared/src/types/index.ts

@@ -9,6 +9,8 @@ export type {
   BastionState,
   VyosVlanSpec,
   VyosInstallSpec,
+  VyosBundle,
+  VyosBundleSetOp,
 } from "./state.js";
 
 export { SUPPORTED_OS, SUPPORTED_ROLES, ROLE_REGISTRY, isValidOsId } from "./state.js";

bastion/src/shared/src/types/state.ts

@@ -88,6 +88,33 @@ export interface VyosVlanSpec {
   vrrp?: string;
 }
 
+/** One config node in a rendered bundle. Mirrors VyosSetOp on the bastion side. */
+export interface VyosBundleSetOp {
+  path: string[];
+  value?: string;
+  /** false appends to a multi-value node (e.g. bond members) instead of replacing. */
+  replace?: boolean;
+}
+
+/**
+ * A router's complete desired config, rendered from the Pulumi model.
+ *
+ * Produced by `kubernetes-deployment/scripts/vyos-render-bundle.ts` from the
+ * same subtree model `pulumi up` applies. The point is that labctl never
+ * authors VyOS config: bring-up replays what Pulumi already declares, so a
+ * freshly installed router and a `pulumi up` cannot disagree.
+ *
+ * Secret values arrive as `@secret:<key>` sentinels and are DROPPED at install
+ * time -- the bundle is committed to git and must stay safe to read. The router
+ * comes up on the LAN without its PPPoE credential; the first `pulumi up`
+ * supplies it. That handoff is deliberate.
+ */
+export interface VyosBundle {
+  sets: VyosBundleSetOp[];
+  /** Paths that are VyOS tag nodes — the installer's ConfigTree needs them marked. */
+  tags: string[][];
+}
+
 /**
  * VyOS-specific install parameters. Rendered into the config.boot that the
  * installer adopts, so the router comes up already configured.
@@ -96,6 +123,31 @@ export interface VyosVlanSpec {
  * PXE cannot run over LACP, so the install-time NIC has to stay unbonded.
  */
 export interface VyosInstallSpec {
+  /**
+   * A complete rendered config for this router. When present it REPLACES the
+   * derived interface/VLAN/VRRP config below -- the bundle already describes
+   * all of it, and deriving a second opinion is exactly the drift this exists
+   * to prevent. The remaining install parameters (password, disk, console) are
+   * still honoured because they are installer inputs, not router config.
+   */
+  bundle?: VyosBundle;
+  /**
+   * Key for the VyOS HTTP API, enabled at install so the router is manageable
+   * from the moment it boots.
+   *
+   * Without this the box comes up reachable only over SSH, and enabling the API
+   * later is a hand-run config change on a live firewall -- which is exactly the
+   * gap that left vyos001/vyos002 unmanageable by Pulumi after their cutover.
+   * The API is deliberately NOT part of the Pulumi model: a provider that
+   * manages its own transport can revoke its own access.
+   */
+  apiKey?: string;
+  /**
+   * Address the API listens on. Defaults to the management address when static.
+   * Never left unbound: an unrestricted listener puts a config-write endpoint on
+   * every segment the router touches, including the WAN.
+   */
+  apiListenAddress?: string;
   /** Interfaces aggregated into bond0 with LACP (802.3ad). Omit for no bond. */
   bondMembers?: string[];
   /** CIDR address on bond0 itself — the switch trunk's native/untagged VLAN. */

bastion/tests/integration/k3s-single-node.test.ts

@@ -161,7 +161,7 @@ EOF'
       CILIUM_CLI_VERSION=$(curl -s https://raw.githubusercontent.com/cilium/cilium-cli/main/stable.txt)
       curl -L --fail --silent "https://github.com/cilium/cilium-cli/releases/download/\${CILIUM_CLI_VERSION}/cilium-linux-amd64.tar.gz" | sudo tar xz -C /usr/local/bin
       DEFAULT_DEV=$(ip -4 route show default | awk '{print $5}' | head -1)
-      sudo KUBECONFIG=/etc/rancher/k3s/k3s.yaml cilium install --set kubeProxyReplacement=true --set ipam.mode=kubernetes --set devices=$DEFAULT_DEV --set nodePort.directRoutingDevice=$DEFAULT_DEV
+      sudo KUBECONFIG=/etc/rancher/k3s/k3s.yaml cilium install --set kubeProxyReplacement=true --set ipam.mode=cluster-pool --set ipam.operator.clusterPoolIPv4PodCIDRList='{10.42.0.0/16}' --set ipam.operator.clusterPoolIPv4MaskSize=24 --set devices=$DEFAULT_DEV --set nodePort.directRoutingDevice=$DEFAULT_DEV
     `.trim(), "cilium install", { keyPath: sshKeyPath, timeout: 120_000 });
 
     log("Waiting for Cilium to be ready...");

labsim/.gitignore

@@ -2,3 +2,7 @@
 *.log
 labsim_matrix_lib.py
 __pycache__/
+
+# Cluster-admin credentials for the rehearsal cluster, written by
+# `k8s-up.sh --kubeconfig`. Regenerate it rather than commit it.
+*.kubeconfig

labsim/README.md

@@ -15,10 +15,27 @@ Each VLAN is its own isolated libvirt network with one tiny Alpine VM on it.
 | 2 | k8s | 172.31.2.0/24 | 172.31.2.10 | 192.168.8.0/23 |
 | 3 | kvm | 172.31.3.0/24 | 172.31.3.10 | 192.168.3.0/24 |
 | 9 | private | 172.31.9.0/24 | 172.31.9.10 | 10.0.9.0/23 |
-| 10 | lot | 172.31.10.0/24 | 172.31.10.10 | 10.0.0.0/23 |
+| 10 | lot | **172.31.10.0/23** | 172.31.10.10 | 10.0.0.0/23 |
 | 200 | roomates | 172.31.200.0/24 | 172.31.200.10 | 192.168.2.0/24 |
 
-The sim subnet always encodes the VLAN id: `172.31.<vlan>.0/24`.
+The sim subnet encodes the VLAN id: `172.31.<vlan>.0/24`, with one exception.
+**VLAN 10 is a `/23`** because every UniFi DHCP reservation lives in LoT and LoT
+spans `10.0.0.x` *and* `10.0.1.x`, which a `/24` cannot hold. The mapping stays
+readable — `10.0.0.46 → 172.31.10.46`, `10.0.1.67 → 172.31.11.67`.
+
+LoT's host leg is `.3`, not `.2`, because `10.0.0.2` is a real reservation
+(Hubitat) that maps onto `172.31.10.2`. `.3` is unreserved and sits below the
+DHCP pool, so it can never be handed out.
+
+`vlans.conf` therefore takes two optional trailing fields:
+
+```
+vlan_id:name:sim_prefix:real_subnet[:masklen][:host_octet]
+```
+
+defaulting to `24` and `2`. k8s and Private are also `/23` in production but
+hold no reservations, so they keep their `/24` and their DHCP range is clamped
+— reported at generation time, never silently.
 
 Address plan, identical on every VLAN:
 
@@ -69,6 +86,54 @@ sudo virsh console labsim-2-k8s     # root / labsim
 ./monitoring-up.sh               # topology page + Prometheus + Grafana
 ```
 
+## Testing the DHCP migration
+
+`./labsim-dhcp-test.sh` boots throwaway VMs whose MACs are **real production
+MACs** and checks each gets the address UniFi reserved for it. MACs are the one
+piece of production config that transplants verbatim, which is what makes this a
+test rather than a rehearsal. It is safe because `ovs-labsim` has no physical
+NIC — verified with `ovs-vsctl show` — so a production MAC cannot reach the real
+LAN.
+
+Apply the config first, from `../migration`:
+
+```bash
+python3 unifi-to-vyos.py --mode sim -o /tmp/sim.conf   # 6 subnets, 31 mappings
+# load onto labsim-vyos, then:
+./labsim-dhcp-test.sh
+```
+
+**Result on VyOS 2026.08 (kea): all four cases pass.** The one that mattered:
+most UniFi reservations sit *inside* the DHCP pool, and **kea honours in-pool
+host reservations** — `printer1` received `172.31.10.46` from within the
+`.10.11–.11.254` pool. That was the open question blocking the cutover.
+
+### The lease database will lie to you
+
+The script wipes `/config/dhcp/dhcp4-leases.csv*` before every run, and both
+halves of that matter:
+
+- **Stale leases defeat reservations.** Re-running against yesterday's leases,
+  kea handed dynamic addresses to three devices that have reservations. The
+  reservation was present and correct in `/run/kea/kea-dhcp4.conf` the whole
+  time. Kea saw the reserved address as already leased to "another client" —
+  same MAC, but a different client-id from the earlier boot — and allocated
+  elsewhere. The cutover itself starts with an empty lease database, so this is
+  a *testing* artifact, but it is worth knowing that a reservation is not an
+  unconditional guarantee once leases exist.
+- **The `*` is load-bearing.** Kea's memfile backend keeps lease-file-cleanup
+  rotations (`dhcp4-leases.csv.2`) and restores from them on start, so
+  truncating only the primary file changes nothing.
+
+Both of those first appeared as a *passing* test. The verdict logic now refuses
+to score a MAC with more than one lease, because taking the first match had
+reported an hours-old lease as the current answer and turned three failures
+into apparent passes.
+
+Still open: whether kea will hand a *reserved* address to a *different* client
+while the reserved device is offline. The negative case here only proves an
+unreserved MAC gets an unreserved address.
+
 - **http://localhost:9101/** — live mesh: a node per VLAN, the router in the
   middle, one line per pair coloured green/red with the ICMP RTT on it. Hover a
   line for per-direction detail. Refreshes every 5s. This is the one to watch
@@ -78,6 +143,167 @@ sudo virsh console labsim-2-k8s     # root / labsim
 - **http://localhost:9101/metrics** — `labsim_reachable{src,dst,proto}` and
   `labsim_rtt_ms{src,dst}`.
 
+## WAN follows VRRP, and the PPPoE half of it
+
+One consumer ISP account, two routers. The 10 gig line's lease is bound to a
+cloned MAC and the Vodafone line to a single credential, so neither can be live
+on both boxes: the WAN has to move with mastership.
+
+The two halves use different control planes, and that asymmetry is the design:
+
+| | plane | why |
+|---|---|---|
+| `bond0.53` | VyOS **config** (`disable`) | only config can move a MAC |
+| `pppoe0` | **systemd** unit gate | see below |
+
+`set interfaces pppoe pppoe0 disable` cannot work as a resting state.
+`interfaces_pppoe.py` treats `disable` and `delete` identically and **unlinks
+`/etc/ppp/peers/pppoe0`** — which is pppd's own options file. The resting state
+therefore destroyed what the promotion path needed, and `ppp@pppoe0`
+restart-looped against it (47 restarts, zero sessions at the AC). It also makes
+op-mode `connect interface pppoe0` refuse, and puts every failover behind a
+priority-322 commit where one unrelated bad node fails the lot.
+
+So `pppoe0` is configured identically and **enabled on both**, and dialling is
+gated by a drop-in:
+
+```ini
+ConditionPathExists=/run/vrrp-wan/may-dial
+ConditionPathExists=/etc/ppp/peers/pppoe0
+```
+
+`/run` is tmpfs, so the gate is shut at boot. That matters more than it looks:
+with the node enabled, `interfaces_pppoe.py` restarts ppp on **every** commit
+touching the pppoe subtree when the daemon isn't running — so the backup
+actively tries to dial whenever anything commits. The gate is the only thing
+making that a no-op, which is why the reconciler refuses to bless a box whose
+drop-in is missing (`/etc` is per-image; a VyOS upgrade would silently remove
+the protection).
+
+`may-dial` is a **lease**, not a flag: `ConditionPathExists` is evaluated at
+start only, so it can prevent a dial but never revoke one. `vrrp-wan-reconcile`
+renews it every 30s; `vrrp-wan-guard` runs every 5s and only ever revokes.
+
+### Testing it
+
+```sh
+./labsim-pppoe-ha-test.sh --all
+```
+
+The verdict is what the **routers** and the **access concentrator** did, never
+what a client happened to get — and the harness refuses to run at all while a
+router still has a default route via `eth2`, because the libvirt-NAT scaffold
+answers connectivity checks that the WAN under test would have failed. The
+invariant it enforces throughout: *the AC never reports two `simdsl` sessions,
+and no two routers ever hold `pppoe0`.*
+
+Two failures the harness itself produced, both worth remembering: waiting for
+"exactly one holder" returns instantly during a handover (it was already true),
+and judging connectivity on a single ping 20s after a link drop reports an
+outage that has already healed. Ask **who** holds it, and poll.
+
+Evidence in `wan-failover-evidence/`.
+
+## Routing: BGP, dual WAN, and the ISP VMs
+
+`sim-ha-config.py` covers the LAN side of the routers. `sim-net-config.py`
+covers everything that makes this a rehearsal for production *routing*:
+
+| role | VM | what it generates |
+|---|---|---|
+| `primary` | `labsim-vyos` | BGP + dual WAN + health-checked failover |
+| `secondary` | `labsim-vyos2` | BGP only |
+| `isp-dhcp` | `labsim-isp-dhcp` | 10gig-equivalent ISP on VLAN 53 |
+| `isp-pppoe` | `labsim-isp-pppoe` | Vodafone-equivalent PPPoE ISP on VLAN 51 |
+
+Both ISP VMs are VyOS with two NICs: one on the OVS trunk facing the sim
+router, one on libvirt's `default` network, NATing customers to the real
+internet. They use RFC 5737 documentation ranges (`203.0.113.0/24`,
+`198.51.100.0/24`) so a leaked sim route cannot blackhole anything real.
+
+```sh
+./sim-net-apply.sh check     # VM state vs what the code says — run this first
+./sim-net-apply.sh apply     # push generated config over the serial console
+```
+
+`check` is the important one. All of this previously existed only as running
+state, applied by hand over SSH; rebuilding a VM lost it, and nothing recorded
+why any of it was shaped the way it was.
+
+### Known gaps vs production
+
+- **WAN is on the primary router only.** Production has WAN on both. Two PPPoE
+  clients sharing one credential against a single access concentrator is a
+  failure mode production does not have, so the sim does not model it. VRRP and
+  conntrack failover are still exercised.
+- **ISP VM interface names are not stable across a rebuild** — `isp-dhcp` came
+  up as `eth0`/`eth1` and `isp-pppoe` as `eth2`/`eth3` from identical XML.
+  Check `show interfaces` and pass `--wan-if` / `--uplink-if` rather than
+  trusting the defaults.
+- **`eth2` on the primary router** is a libvirt-NAT uplink predating the ISP
+  VMs: a third default route with no production equivalent that masks real WAN
+  failures during a failover test. `--drop-scaffold` removes it.
+- **Committing on `isp-pppoe` drops the router's PPPoE session**, and the
+  client does not redial promptly. After any change there, check `pppoe0` on
+  the router and `sudo systemctl restart ppp@pppoe0` if it is missing.
+
+## The trunk carries every VLAN tagged, including Management
+
+There is deliberately **no native/untagged VLAN** on the trunks to the routers,
+and Management lives on `bond0.1`, not on the bare `bond0`.
+
+A native VLAN is what puts a subnet on the bond **parent** while every other
+VLAN sits on a sub-interface of it. With `dhcp-socket-type: raw`, kea receives
+each tagged frame *twice* — once on the sub-interface and once on the parent —
+and answers from the parent's pool as well (ISC Kea
+[#1117](https://gitlab.isc.org/isc-projects/kea/-/issues/1117)). A client on
+VLAN 3 gets two OFFERs and keeps whichever arrives first:
+
+```
+bond0.3 :  172.31.3.252 → 172.31.3.11   correct
+bond0   :  172.31.1.252 → 172.31.1.8    UNTAGGED, Management pool, wrong
+```
+
+`./labsim-vlan-leak-test.sh` makes one client on a tagged VLAN send a DISCOVER
+and captures on the parent and the sub-interface at once. The verdict is how
+many OFFERs the **server** emitted and from which subnets — deliberately not
+"did the client get the right address", because a client picking correctly is
+exactly how this hid. Both orderings were observed across runs, so a passing
+client proves nothing.
+
+```sh
+./labsim-vlan-leak-test.sh --vlan 3           # PASS on the current shape
+LABSIM_NATIVE_VLAN=1 ./router-up.sh           # restore the old shape...
+./labsim-vlan-leak-test.sh --vlan 3           # ...and it FAILs again
+```
+
+Three things this cost, all of which apply to production:
+
+- **Kea must be restarted after the address moves.** VyOS does not restart it
+  for an interface address change, so it keeps a raw socket bound with the old
+  address and the bug survives the fix. In the sim kea had been running since
+  16 Aug; the first post-fix test failed for this reason alone and looked like
+  the fix simply not working.
+- **The firewall interface-group must move too.** `interface-group LAN` named
+  the bare `bond0`; with a default-deny ruleset, moving the address without
+  moving the group drops every management session and all VLAN 1 routing.
+- **Duplicate delivery does not stop.** #1117 says only that there is no longer
+  a subnet on the parent to match, and that is exactly what happens: two replies
+  per DISCOVER, both now from the correct pool. Harmless, but do not read a
+  duplicate as a failure.
+
+### Tagged and untagged Management coexist
+
+Verified directly, and it is what makes the production cutover a rolling change
+rather than an outage: with the primary still untagged on `bond0` and the
+secondary already tagged on `bond0.1`, both routers were reachable, the VIP
+stayed up and a VLAN 1 client kept its gateway. One VLAN is one broadcast
+domain regardless of how each port tags it, so the two firewalls can be
+converted one at a time. See `migration/MANAGEMENT-VLAN-TAGGED.md`.
+
+`./vlan1-move-monitor.sh` logs VIP/router liveness once a second during the
+change, because VRRP reconverges and leaves no trace of who held the VIP.
+
 ## Notes for whoever extends this
 
 Things that cost time the first time round, all verified on this image:
@@ -98,7 +324,14 @@ Things that cost time the first time round, all verified on this image:
 
 ## Not modelled (yet)
 
-VLANs are separate L2 segments rather than one 802.1Q trunk, so this exercises
-inter-VLAN routing but not a `bond0.<vif>` trunk config specifically. A router
-VM would attach one NIC per VLAN. Adding a tagged-trunk variant is the obvious
-next step if the bond/vif config itself needs testing.
+- **The secondary's bond was fiction until 2026-09-02.** `ovs_bond_router`'s
+  "already bonded, nothing to do" check compared only the trunk VLAN list, not
+  the membership. Restarting a VM recreates its taps under new names, so the
+  bond sat there holding two interfaces that no longer existed while the router's
+  real taps ran in the bridge as two *independent* ports — no LACP, and carrying
+  libvirt's own portgroup VLAN config rather than the bond's. It reconciles
+  membership now, but the lesson generalises: a sim that reports success is not
+  the same as a sim that models the thing.
+- **`labsim-vyos` has a third NIC** on libvirt's `default` network (the scaffold
+  uplink, see `--drop-scaffold`). The tap count is filtered to `$OVS_NET` for
+  that reason; an unfiltered count is 3 and silently skipped the primary's bond.

labsim/cilium-ipam-switch.sh

@@ -0,0 +1,144 @@
+#!/usr/bin/env bash
+# Procedure around a Cilium IPAM mode change. Works against any cluster, so the
+# rehearsal in labsim and the real thing in production run the SAME steps.
+#
+# It deliberately does NOT change the mode itself. In labsim that is `helm
+# upgrade`; in production Pulumi owns the release and a script racing it would
+# just reintroduce drift. What this owns is everything around the apply -- the
+# evidence, the deadlock, and the verdict.
+#
+#   ./cilium-ipam-switch.sh preflight   record what the cluster looks like now
+#   ./cilium-ipam-switch.sh unstick     break the agent-not-ready taint deadlock
+#   ./cilium-ipam-switch.sh verify      compare against preflight, report renumbering
+#
+#   KUBECONFIG=... ./cilium-ipam-switch.sh preflight
+#
+# Whether a recycle is needed is CONDITIONAL, and `verify` is what decides it.
+#
+# The operator does not preserve which node held which /24 -- it adopts whatever
+# CiliumNode.spec.ipam.podCIDRs already says. So:
+#
+#   * If CiliumNode already agrees with node.spec.podCIDRs on every node -- which
+#     is the case for any cluster that has only ever run ipam=kubernetes, because
+#     the operator syncs one from the other -- the pool adopts the existing
+#     allocation, no node is renumbered, and NO pod recycle is needed. Verified
+#     on the 3-node labsim cluster: CIDRs unchanged, nothing stranded, the only
+#     blip was the cilium DaemonSet restarting itself.
+#
+#   * If the two sources DISAGREE, nodes can swap /24s. Their running pods keep
+#     addresses that no longer fall inside the node's range, every other node
+#     routes that prefix to the wrong node, and those pods go unreachable
+#     cross-node while still showing Running. Then a full recycle is mandatory.
+#
+# Do not skip `verify` on the assumption of the good case. Run it and read it.
+set -uo pipefail
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+STATE="${STATE:-$SCRIPT_DIR/.ipam-switch-state}"
+K="kubectl"
+
+say()  { printf '\033[0;36m[ipam]\033[0m %s\n' "$*"; }
+warn() { printf '\033[1;33m[ipam]\033[0m %s\n' "$*" >&2; }
+
+snapshot() {
+  echo "## nodes"
+  $K get nodes -o jsonpath='{range .items[*]}{.metadata.name}{"\t"}{.spec.podCIDRs}{"\n"}{end}' 2>/dev/null
+  echo "## ciliumnodes"
+  $K get ciliumnode -o jsonpath='{range .items[*]}{.metadata.name}{"\t"}{.spec.ipam.podCIDRs}{"\n"}{end}' 2>/dev/null
+  echo "## pods"
+  $K get pods -A -o jsonpath='{range .items[*]}{.metadata.namespace}/{.metadata.name}{"\t"}{.status.podIP}{"\n"}{end}' 2>/dev/null \
+    | grep -vP '\t$' | sort
+  echo "## ipam"
+  $K -n kube-system get cm cilium-config -o jsonpath='{.data.ipam}' 2>/dev/null; echo
+}
+
+cmd_preflight() {
+  mkdir -p "$STATE"
+  snapshot > "$STATE/before.txt"
+  say "recorded $(grep -c . "$STATE/before.txt") lines -> $STATE/before.txt"
+  say "mode now: $(sed -n '/^## ipam/,$p' "$STATE/before.txt" | tail -1)"
+  # The pod inventory is the rollback reference: if the switch renumbers, this
+  # is the only record of what an address USED to be.
+  say "pods on the pod network: $(sed -n '/^## pods/,/^## ipam/p' "$STATE/before.txt" | grep -c '10\.')"
+}
+
+# The deadlock, in one place because it WILL happen and doing it by hand under
+# time pressure is how the wrong node gets untainted:
+#   agent has no pod CIDR -> agent not ready -> node keeps
+#   node.cilium.io/agent-not-ready:NoSchedule -> the operator that would assign
+#   the CIDR cannot schedule -> agent still has no pod CIDR.
+# Removing the taint is safe: it exists to keep normal workloads off a node
+# without working networking, and the operator is precisely the thing that fixes
+# that. Kubernetes re-adds it on the next agent restart.
+cmd_unstick() {
+  local stuck=0
+  for n in $($K get nodes -o name 2>/dev/null); do
+    $K get "$n" -o jsonpath='{.spec.taints[*].key}' 2>/dev/null | grep -q 'agent-not-ready' || continue
+    warn "${n#node/} carries agent-not-ready; removing so the operator can schedule"
+    $K taint "$n" node.cilium.io/agent-not-ready- >/dev/null 2>&1 && stuck=$((stuck+1))
+  done
+  [ "$stuck" -eq 0 ] && say "no node was stuck" || say "cleared $stuck node(s)"
+  local pend
+  pend="$($K -n kube-system get pods -l io.cilium/app=operator --no-headers 2>/dev/null | grep -c Pending)"
+  [ "${pend:-0}" -gt 0 ] && warn "$pend operator pod(s) still Pending — check tolerations, not just taints"
+  return 0
+}
+
+cmd_verify() {
+  [ -f "$STATE/before.txt" ] || { warn "no preflight snapshot; nothing to compare"; return 1; }
+  snapshot > "$STATE/after.txt"
+  echo
+  say "mode: $(sed -n '/^## ipam/,$p' "$STATE/before.txt" | tail -1) -> $(sed -n '/^## ipam/,$p' "$STATE/after.txt" | tail -1)"
+
+  # The question that decides the size of the maintenance window: did per-node
+  # CIDRs survive, or was every node renumbered (and every pod with it)?
+  local moved=0
+  while IFS=$'\t' read -r node cidr; do
+    [ -z "${node:-}" ] && continue
+    local now; now="$(sed -n '/^## ciliumnodes/,/^## pods/p' "$STATE/after.txt" | awk -F'\t' -v n="$node" '$1==n{print $2}')"
+    if [ -n "$now" ] && [ "$now" != "$cidr" ]; then
+      printf '    %-16s %s -> %s\n' "$node" "$cidr" "$now"; moved=$((moved+1))
+    fi
+  done < <(sed -n '/^## ciliumnodes/,/^## pods/p' "$STATE/before.txt" | grep -P '\t')
+  if [ "$moved" -eq 0 ]; then
+    say "per-node CIDRs UNCHANGED — the pool adopted the existing allocation"
+  else
+    warn "$moved node(s) renumbered — every pod on them must be recycled"
+  fi
+
+  local before after same
+  before="$(sed -n '/^## pods/,/^## ipam/p' "$STATE/before.txt" | grep -P '\t10\.' | wc -l)"
+  after="$(sed -n '/^## pods/,/^## ipam/p' "$STATE/after.txt"  | grep -P '\t10\.' | wc -l)"
+  same="$(comm -12 <(sed -n '/^## pods/,/^## ipam/p' "$STATE/before.txt" | grep -P '\t10\.' | sort) \
+                   <(sed -n '/^## pods/,/^## ipam/p' "$STATE/after.txt"  | grep -P '\t10\.' | sort) | wc -l)"
+  say "pods: $before before, $after after, $same kept the SAME address"
+  # Keeping the address is NOT the good outcome. If a node's CIDR moved, its
+  # existing pods keep IPs that no longer fall inside it, every other node routes
+  # that prefix to the WRONG node, and those pods go unreachable cross-node while
+  # looking perfectly healthy. Observed in labsim: two nodes swapped CIDRs and
+  # cross-node ping to their pods dropped 100%, with every pod still Running.
+  # This is the check that decides whether a recycle is optional or mandatory.
+  local stranded=0
+  while read -r ns name ip node; do
+    [ -z "${node:-}" ] && continue
+    local cidr; cidr="$($K get ciliumnode "$node" -o jsonpath='{.spec.ipam.podCIDRs[0]}' 2>/dev/null)"
+    [ -z "$cidr" ] && continue
+    case "$ip" in
+      "${cidr%.*/*}".*) ;;
+      *) printf '    STRANDED %-40s %-15s on %s (now %s)\n' "$ns/$name" "$ip" "$node" "$cidr"; stranded=$((stranded+1)) ;;
+    esac
+  done < <($K get pods -A -o jsonpath='{range .items[?(@.status.podIP)]}{.metadata.namespace}{" "}{.metadata.name}{" "}{.status.podIP}{" "}{.spec.nodeName}{"\n"}{end}' 2>/dev/null | grep -E ' 10\.')
+  if [ "$stranded" -gt 0 ]; then
+    warn "$stranded pod(s) sit OUTSIDE their node CIDR — unreachable cross-node until recycled"
+    warn "recycle: for ns in $(kubectl get ns -o name | cut -d/ -f2); do kubectl -n $ns rollout restart deploy,ds,sts 2>/dev/null; done"
+  else
+    say "every pod is inside its node CIDR — no recycle needed"
+  fi
+  say "not-Running pods: $($K get pods -A --no-headers 2>/dev/null | grep -vcE 'Running|Completed')"
+}
+
+case "${1:-}" in
+  preflight) cmd_preflight ;;
+  unstick)   cmd_unstick ;;
+  verify)    cmd_verify ;;
+  *) sed -n '2,16p' "$0"; exit 1 ;;
+esac

labsim/console-apply.py

@@ -0,0 +1,116 @@
+#!/usr/bin/env python3
+"""Apply VyOS config to a labsim VM over its serial console.
+
+Needed because a freshly installed VyOS comes up holding the same addresses as
+its peer, so there is a window where it cannot safely be reached over the
+network at all. The console does not care.
+
+  ./console-apply.py --vm labsim-vyos2 --config r2.conf
+"""
+from __future__ import annotations
+
+import argparse
+import sys
+import time
+
+import pexpect
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--vm", required=True)
+    ap.add_argument("--config", required=True)
+    ap.add_argument("--user", default="vyos")
+    ap.add_argument("--password", default="vyos")
+    # `save` writes config.boot. For WAN work that is dangerous: the resting
+    # state must stay `vif 53 disable` on both routers, and saving while a box
+    # is master persists the ENABLED state -- so a reboot would have it claim
+    # the cloned MAC. Observed in labsim on 2026-09-02.
+    ap.add_argument("--no-save", action="store_true",
+                    help="commit without saving (leave config.boot untouched)")
+    args = ap.parse_args()
+
+    cmds = [l.rstrip() for l in open(args.config)
+            if l.strip() and not l.lstrip().startswith("#")]
+    print(f"{len(cmds)} commands to apply to {args.vm}", file=sys.stderr)
+
+    c = pexpect.spawn(f"virsh --connect qemu:///system console {args.vm}",
+                      timeout=90, encoding="utf-8")
+    c.logfile_read = None
+    c.sendline("")
+    time.sleep(2)
+    c.sendline("")
+
+    # Log in. A freshly booted box may still be starting services, so allow a
+    # generous window and re-prod the console rather than failing on the first
+    # miss.
+    #
+    # `# ` matters as much as `$ `: a previous run that died mid-config leaves
+    # the console sitting in configuration mode, and waiting only for the
+    # operational prompt then hangs forever against a perfectly healthy VM.
+    in_config = False
+    for _ in range(40):
+        i = c.expect([r"login:", r"\$ ", r"# ", pexpect.TIMEOUT], timeout=15)
+        if i == 0:
+            c.sendline(args.user)
+            c.expect("Password:", timeout=30)
+            c.sendline(args.password)
+            c.expect([r"\$ ", r"# "], timeout=60)
+            break
+        if i == 1:
+            break
+        if i == 2:
+            in_config = True
+            break
+        c.sendline("")
+    else:
+        print("never reached a prompt", file=sys.stderr)
+        return 1
+
+    if in_config:
+        # Drop whatever the previous run left half-built rather than committing
+        # a candidate nobody has seen.
+        print("console was left in config mode; discarding stale candidate",
+              file=sys.stderr)
+        c.sendline("discard")
+        c.expect(r"# ", timeout=60)
+    else:
+        c.sendline("configure")
+        c.expect(r"# ", timeout=60)
+
+    for cmd in cmds:
+        c.sendline(cmd)
+        c.expect(r"# ", timeout=60)
+        out = c.before or ""
+        if "Set failed" in out or "not valid" in out or "Invalid" in out:
+            print(f"FAILED: {cmd}\n  {out.strip()[:200]}", file=sys.stderr)
+
+    print("committing...", file=sys.stderr)
+    c.sendline("commit")
+    c.expect(r"# ", timeout=300)
+    commit_out = c.before or ""
+    if not args.no_save:
+        c.sendline("save")
+        c.expect(r"# ", timeout=120)
+    # Accept either prompt on the way out. Insisting on `$ ` here hangs against
+    # a healthy box -- and worse, leaves the console parked in config mode, so
+    # the NEXT run finds a `# ` it was not expecting either. One strict expect
+    # turned into two failures.
+    c.sendline("exit")
+    c.expect([r"\$ ", r"# ", pexpect.TIMEOUT], timeout=60)
+    c.sendline("exit")
+    c.close(force=True)
+
+    bad = [l for l in commit_out.splitlines()
+           if "failed" in l.lower() or "error" in l.lower()]
+    if bad:
+        print("commit reported:", file=sys.stderr)
+        for l in bad[:10]:
+            print(f"  {l.strip()}", file=sys.stderr)
+        return 1
+    print("committed and saved", file=sys.stderr)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())

labsim/dualstack-lab.sh

@@ -0,0 +1,318 @@
+#!/usr/bin/env bash
+# Differential study: what ACTUALLY differs between a k3s cluster born
+# dual-stack and one converted in place?
+#
+# k3s says dual-stack "cannot be enabled on an existing cluster". The stated
+# reason is narrow -- nodes get Pod CIDRs only at join and the Kubernetes IPAM
+# controller will not hand out a new IPv6 CIDR later -- and it does not obviously
+# apply to a cluster where Cilium owns IPAM. Rather than argue from docs, build
+# both shapes and diff them.
+#
+#   ./dualstack-lab.sh up v4         single-node k3s, IPv4 only     (.21)
+#   ./dualstack-lab.sh up dual       single-node k3s, dual-stack    (.22)
+#   ./dualstack-lab.sh pristine v4   reflink copy of v4's disk, so the upgrade
+#                                    attempt can be rolled back and retried
+#   ./dualstack-lab.sh restore v4    put that copy back
+#   ./dualstack-lab.sh collect <n>   normalized state dump -> evidence/<n>/
+#   ./dualstack-lab.sh compare a b   semantic diff of two collections
+#   ./dualstack-lab.sh virtdiff a b  whole-filesystem diff, offline (libguestfs)
+#   ./dualstack-lab.sh down [name]
+#
+# The comparison that matters is `compare dual upgraded`: everything it prints
+# is a way the converted cluster failed to reach the shape of a native one.
+#
+# Single node on purpose. Dual-stack is decided by server flags and CNI config,
+# both of which a one-node cluster exercises fully, and it rebuilds in minutes.
+# Node-rejoin behaviour needs the 3-node cluster and is a separate question.
+set -euo pipefail
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+source "$SCRIPT_DIR/lib.sh"
+source "$SCRIPT_DIR/ovs.sh"
+
+K8S_VLAN="${K8S_VLAN:-2}"
+DS_PREFIX="${DS_PREFIX:-172.31.2}"
+MEM="${MEM:-4096}"; CPUS="${CPUS:-2}"; DISK_GB="${DISK_GB:-12}"
+TOKEN="${TOKEN:-labsim-ds-token}"
+CILIUM_VERSION="${CILIUM_VERSION:-1.19.1}"   # same as production
+DEB_BASE="${DEB_BASE:-$IMG_DIR/debian-13-genericcloud-amd64.qcow2}"
+EVIDENCE="$SCRIPT_DIR/dualstack-evidence"
+
+# Pod/Service ranges. IPv4 halves are k3s's own defaults, so the v4-only build is
+# a stock cluster and the diff is not polluted by gratuitous differences.
+# IPv6 halves are ULA: this cluster never routes off-box, and using the real /48
+# here would put lab addresses into a prefix that production also announces.
+V4_CLUSTER="10.42.0.0/16"; V4_SERVICE="10.43.0.0/16"
+V6_CLUSTER="${V6_CLUSTER:-fd00:42::/56}"
+V6_SERVICE="${V6_SERVICE:-fd00:43::/112}"   # /112 -- apiserver caps v6 service ranges
+V6_PREFIX="${V6_PREFIX:-fd00:2}"            # node addresses: fd00:2::<octet>
+
+vm_name() { echo "labsim-ds-$1"; }
+vm_ip()   { case "$1" in v4) echo "$DS_PREFIX.21";; dual) echo "$DS_PREFIX.22";; *) die "unknown build '$1'";; esac; }
+vm_ip6()  { case "$1" in v4) echo "$V6_PREFIX::21";; dual) echo "$V6_PREFIX::22";; *) die "unknown build '$1'";; esac; }
+disk_of() { echo "$IMG_DIR/$(vm_name "$1").qcow2"; }
+
+ssh_vm() { local ip="$1"; shift; ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null \
+             -o LogLevel=ERROR -o ConnectTimeout=8 -o BatchMode=yes "debian@$ip" "$@"; }
+
+# --- seed -----------------------------------------------------------------
+build_seed() {
+  local iso="$1" vm="$2" mode="$3" pubkey="$4"
+  local ip ip6 tmp; ip="$(vm_ip "$mode")"; ip6="$(vm_ip6 "$mode")"; tmp="$(mktemp -d)"
+
+  echo "instance-id: $vm" > "$tmp/meta-data"
+  # Static v6 on both builds. The v4-only cluster still gets an IPv6 ADDRESS --
+  # only its Kubernetes config is v4-only. Otherwise the diff would be dominated
+  # by host addressing rather than by what Kubernetes did differently.
+  cat > "$tmp/network-config" <<EOF
+version: 2
+ethernets:
+  enp1s0:
+    addresses: [${ip}/24, ${ip6}/64]
+    routes:
+      - to: default
+        via: ${DS_PREFIX}.1
+    nameservers:
+      addresses: [8.8.8.8, 1.1.1.1]
+EOF
+
+  local exec_args="server --flannel-backend=none --disable-network-policy --disable=servicelb --disable=traefik --tls-san=$ip --cluster-init"
+  if [ "$mode" = dual ]; then
+    exec_args="$exec_args --cluster-cidr=${V4_CLUSTER},${V6_CLUSTER} --service-cidr=${V4_SERVICE},${V6_SERVICE} --node-ip=${ip},${ip6}"
+  else
+    exec_args="$exec_args --node-ip=${ip}"
+  fi
+
+  cat > "$tmp/user-data" <<EOF
+#cloud-config
+hostname: $vm
+fqdn: $vm
+users:
+  - name: debian
+    groups: [sudo]
+    shell: /bin/bash
+    sudo: ["ALL=(ALL) NOPASSWD:ALL"]
+    lock_passwd: false
+    plain_text_passwd: labsim
+    ssh_authorized_keys: [$pubkey]
+ssh_pwauth: true
+disable_root: false
+package_update: true
+packages: [curl, jq, iproute2, nftables]
+write_files:
+  - path: /etc/modules-load.d/cilium.conf
+    content: |
+      br_netfilter
+  - path: /etc/dualstack-lab-mode
+    content: |
+      $mode
+runcmd:
+  - modprobe br_netfilter || true
+  - |
+    curl -sfL https://get.k3s.io | INSTALL_K3S_EXEC="$exec_args" K3S_TOKEN="$TOKEN" sh -
+  - |
+    # Cilium via helm, matching the production version. IPAM stays 'kubernetes'
+    # in BOTH builds on purpose: that is what production runs, and it is the
+    # mode the k3s objection is actually about. If the converted cluster needs
+    # cluster-pool to work, the diff should be what tells us so.
+    curl -sfL https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3 | bash || true
+    export KUBECONFIG=/etc/rancher/k3s/k3s.yaml
+    helm repo add cilium https://helm.cilium.io >/dev/null 2>&1 || true
+    helm repo update >/dev/null 2>&1 || true
+    for i in \$(seq 1 60); do kubectl get nodes >/dev/null 2>&1 && break; sleep 5; done
+    if [ "$mode" = dual ]; then
+      helm install cilium cilium/cilium --version $CILIUM_VERSION -n kube-system \\
+        --set kubeProxyReplacement=false --set ipam.mode=kubernetes \\
+        --set ipv4.enabled=true --set ipv6.enabled=true \\
+        --set k8sServiceHost=$ip --set k8sServicePort=6443 || true
+    else
+      helm install cilium cilium/cilium --version $CILIUM_VERSION -n kube-system \\
+        --set kubeProxyReplacement=false --set ipam.mode=kubernetes \\
+        --set ipv4.enabled=true --set ipv6.enabled=false \\
+        --set k8sServiceHost=$ip --set k8sServicePort=6443 || true
+    fi
+    touch /etc/dualstack-lab-ready
+EOF
+  sudo mkdir -p "$(dirname "$iso")"
+  sudo genisoimage -quiet -output "$iso" -volid cidata -joliet -rock \
+    "$tmp/user-data" "$tmp/meta-data" "$tmp/network-config"
+  rm -rf "$tmp"
+}
+
+cmd_up() {
+  local mode="${1:?usage: up <v4|dual>}"
+  local vm ip disk seed pubkey
+  vm="$(vm_name "$mode")"; ip="$(vm_ip "$mode")"; disk="$(disk_of "$mode")"
+  seed="$IMG_DIR/${vm}-seed.iso"; pubkey="$(find_ssh_pubkey)"
+
+  [ -f "$DEB_BASE" ] || die "base image missing: $DEB_BASE (run ./k8s-up.sh once)"
+  if virsh_q dominfo "$vm" >/dev/null 2>&1; then
+    log "$vm exists — starting if stopped"
+    [ "$(virsh_q domstate "$vm" | head -1)" = "running" ] || virsh_q start "$vm" >/dev/null
+    return
+  fi
+  selected_vlans; ovs_up
+  log "creating $vm ($mode) at $ip / $(vm_ip6 "$mode")"
+  sudo qemu-img create -q -f qcow2 -F qcow2 -b "$DEB_BASE" "$disk" "${DISK_GB}G" >/dev/null
+  build_seed "$seed" "$vm" "$mode" "$pubkey"
+  sudo virt-install --connect "$LIBVIRT_URI" --name "$vm" \
+    --memory "$MEM" --vcpus "$CPUS" \
+    --disk "path=$disk,format=qcow2,bus=virtio" \
+    --disk "path=$seed,device=cdrom" \
+    --network "network=$OVS_NET,portgroup=vlan${K8S_VLAN},model=virtio" \
+    --os-variant debian12 --graphics none --noautoconsole --import >/dev/null
+  log "installing in background; watch: ssh debian@$ip 'ls /etc/dualstack-lab-ready'"
+}
+
+# --- pristine copy / restore ---------------------------------------------
+# reflink so the copy is instant and independent on btrfs/xfs. A qcow2 backing
+# chain would be cheaper still but makes the parent read-only in practice: boot
+# the parent again and every child silently corrupts.
+cmd_pristine() {
+  local mode="${1:?usage: pristine <v4|dual>}" vm disk
+  vm="$(vm_name "$mode")"; disk="$(disk_of "$mode")"
+  [ "$(virsh_q domstate "$vm" 2>/dev/null | head -1)" = "running" ] && \
+    die "$vm is running — shut it down first (virsh shutdown $vm), a copy of a live disk is not consistent"
+  sudo cp --reflink=auto "$disk" "${disk}.pristine"
+  log "pristine copy: ${disk}.pristine"
+}
+cmd_restore() {
+  local mode="${1:?usage: restore <v4|dual>}" vm disk
+  vm="$(vm_name "$mode")"; disk="$(disk_of "$mode")"
+  [ -f "${disk}.pristine" ] || die "no pristine copy for $mode"
+  [ "$(virsh_q domstate "$vm" 2>/dev/null | head -1)" = "running" ] && \
+    die "$vm is running — shut it down first"
+  sudo cp --reflink=auto "${disk}.pristine" "$disk"
+  log "restored $mode from pristine"
+}
+
+
+# --- the experiment ------------------------------------------------------
+# Convert the IPv4-only cluster in place, mirroring the flags the native build
+# was BORN with. Each step prints what the cluster did, because the interesting
+# output is which step refuses rather than whether the end state is pretty.
+cmd_upgrade() {
+  local ip; ip="$(vm_ip v4)"; local ip6; ip6="$(vm_ip6 v4)"
+  log "step 1/4: add dual CIDRs + dual node-ip to the k3s unit"
+  # Done with python on the box, not nested sed: quoting a multi-line systemd
+  # continuation through ssh -> sh -> sed produced a literal \\n in the unit, and
+  # k3s then saw a dual cluster-cidr with a still-IPv4 service-cidr and refused
+  # to start. All three flags go on one line -- systemd does not care, and there
+  # is nothing left to escape.
+  ssh_vm "$ip" "sudo python3 - <<'PYEOF'
+import re
+u = '/etc/systemd/system/k3s.service'
+s = open(u).read()
+old = \"'--node-ip=${ip}'\"
+new = \"'--cluster-cidr=${V4_CLUSTER},${V6_CLUSTER}' '--service-cidr=${V4_SERVICE},${V6_SERVICE}' '--node-ip=${ip},${ip6}'\"
+assert old in s, 'node-ip flag not found in unit'
+open(u,'w').write(s.replace(old, new))
+print('    unit rewritten')
+PYEOF
+sudo systemctl daemon-reload" || die "unit edit failed"
+  ssh_vm "$ip" "grep -oE \"'--(cluster|service)-cidr=[^']*'|'--node-ip=[^']*'\" /etc/systemd/system/k3s.service | sed 's/^/    /'"
+
+  log "step 2/4: restart k3s and see whether it accepts the changed ranges"
+  ssh_vm "$ip" "sudo systemctl restart k3s" || true
+  for i in $(seq 1 40); do
+    ssh_vm "$ip" "sudo k3s kubectl get --raw /readyz >/dev/null 2>&1" && break
+    sleep 5
+  done
+  ssh_vm "$ip" "sudo journalctl -u k3s --since '2 min ago' --no-pager 2>/dev/null | grep -iE 'cidr|dual|ipv6|invalid|cannot|fail' | tail -12 | sed 's/^/    /'" || true
+
+  log "step 3/4: what the API says now"
+  ssh_vm "$ip" "echo -n '    servicecidr: '; sudo k3s kubectl get servicecidr -o jsonpath='{.items[*].spec.cidrs}'; echo; \
+                echo -n '    node podCIDRs: '; sudo k3s kubectl get node -o jsonpath='{.items[0].spec.podCIDRs}'; echo; \
+                echo -n '    node addresses: '; sudo k3s kubectl get node -o jsonpath='{.items[0].status.addresses[*].address}'; echo" || true
+
+  log "step 4/4: turn on IPv6 in Cilium"
+  ssh_vm "$ip" "export KUBECONFIG=/etc/rancher/k3s/k3s.yaml; sudo -E helm upgrade cilium cilium/cilium --version ${CILIUM_VERSION} -n kube-system --reuse-values --set ipv6.enabled=true >/dev/null 2>&1 && echo '    cilium upgraded' || echo '    cilium upgrade FAILED'" || true
+  ssh_vm "$ip" "sudo k3s kubectl -n kube-system rollout restart ds/cilium >/dev/null 2>&1; sleep 20; sudo k3s kubectl -n kube-system get pods -l k8s-app=cilium --no-headers | sed 's/^/    /'" || true
+  log "now: ./dualstack-lab.sh collect upgraded ${ip} && ./dualstack-lab.sh compare dual upgraded"
+}
+
+# --- evidence collection --------------------------------------------------
+# Normalized on purpose. Two independently built clusters differ in certs,
+# tokens, UUIDs, timestamps and log lines; left raw, that noise buries the
+# handful of differences that actually mean something.
+cmd_collect() {
+  local name="${1:?usage: collect <name> [ip]}"
+  local ip="${2:-}"
+  [ -n "$ip" ] || ip="$(vm_ip "$name" 2>/dev/null || true)"
+  [ -n "$ip" ] || die "collect: give an ip for a non-standard name"
+  local out="$EVIDENCE/$name"; mkdir -p "$out"
+  log "collecting from $name ($ip) -> $out"
+
+  ssh_vm "$ip" 'sudo cat /etc/rancher/k3s/config.yaml 2>/dev/null; sudo systemctl cat k3s 2>/dev/null | grep -A30 ExecStart' \
+    > "$out/k3s-config.txt" 2>/dev/null || true
+  ssh_vm "$ip" 'sudo tr "\0" "\n" < /proc/$(pgrep -f "k3s server" | head -1)/cmdline | grep -v "^$"' \
+    > "$out/k3s-cmdline.txt" 2>/dev/null || true
+  ssh_vm "$ip" 'ip -o addr show | awk "{print \$2, \$3, \$4}"; echo ---; ip -4 route show; echo ---; ip -6 route show' \
+    > "$out/host-net.txt" 2>/dev/null || true
+  ssh_vm "$ip" 'sudo sysctl -a 2>/dev/null | grep -E "net\.ipv6\.conf\.(all|default)\.(forwarding|disable_ipv6)|net\.ipv4\.ip_forward"' \
+    > "$out/sysctl.txt" 2>/dev/null || true
+
+  local K='sudo k3s kubectl'
+  ssh_vm "$ip" "$K get servicecidr -o yaml"       > "$out/servicecidr.yaml" 2>/dev/null || true
+  ssh_vm "$ip" "$K get nodes -o yaml"             > "$out/nodes.yaml.raw"   2>/dev/null || true
+  ssh_vm "$ip" "$K get ciliumnodes -o yaml"       > "$out/ciliumnodes.yaml.raw" 2>/dev/null || true
+  ssh_vm "$ip" "$K -n kube-system get cm cilium-config -o yaml" > "$out/cilium-config.yaml.raw" 2>/dev/null || true
+  ssh_vm "$ip" "$K get svc -A -o custom-columns=NS:.metadata.namespace,NAME:.metadata.name,FAMILYPOLICY:.spec.ipFamilyPolicy,FAMILIES:.spec.ipFamilies,IPS:.spec.clusterIPs" \
+    > "$out/services.txt" 2>/dev/null || true
+  ssh_vm "$ip" "$K get pods -A -o custom-columns=NS:.metadata.namespace,NAME:.metadata.name,IPS:.status.podIPs" \
+    > "$out/podips.txt" 2>/dev/null || true
+
+  # Strip the things that differ every build regardless of configuration.
+  for f in "$out"/*.raw; do
+    [ -e "$f" ] || continue
+    sed -E \
+      -e 's/[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9:]+Z?/<TIME>/g' \
+      -e 's/(uid|resourceVersion|creationTimestamp|generation|observedGeneration): .*/\1: <X>/' \
+      -e 's/[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}/<UUID>/g' \
+      -e 's/(LS0tLS1|[A-Za-z0-9+\/]{60,}=*)/<B64>/g' \
+      "$f" > "${f%.raw}"
+    rm -f "$f"
+  done
+  log "collected $(ls "$out" | wc -l) artefacts"
+}
+
+cmd_compare() {
+  local a="${1:?usage: compare <a> <b>}" b="${2:?}"
+  [ -d "$EVIDENCE/$a" ] && [ -d "$EVIDENCE/$b" ] || die "collect both first"
+  echo "### semantic diff: $a (<) vs $b (>)"
+  diff -ru "$EVIDENCE/$a" "$EVIDENCE/$b" || true
+}
+
+cmd_virtdiff() {
+  local a="${1:?usage: virtdiff <a> <b>}" b="${2:?}"
+  for m in "$a" "$b"; do
+    [ "$(virsh_q domstate "$(vm_name "$m")" 2>/dev/null | head -1)" = "running" ] && \
+      die "$(vm_name "$m") is running — virt-diff needs the disks quiescent"
+  done
+  log "whole-filesystem diff (slow); noise is expected — use it to find what the collector missed"
+  sudo virt-diff -a "$(disk_of "$a")" -A "$(disk_of "$b")" \
+    | grep -vE '/(var/log|tmp|run|proc|sys)/|\.log$|/var/lib/rancher/k3s/(server/(tls|cred|db)|agent)' || true
+}
+
+cmd_down() {
+  local only="${1:-}"
+  for m in v4 dual; do
+    [ -n "$only" ] && [ "$only" != "$m" ] && continue
+    local vm; vm="$(vm_name "$m")"
+    virsh_q dominfo "$vm" >/dev/null 2>&1 || continue
+    log "removing $vm"
+    virsh_q destroy "$vm" >/dev/null 2>&1 || true
+    virsh_q undefine "$vm" --remove-all-storage >/dev/null 2>&1 || true
+  done
+}
+
+case "${1:-}" in
+  up)       shift; cmd_up "$@" ;;
+  upgrade)  shift; cmd_upgrade "$@" ;;
+  pristine) shift; cmd_pristine "$@" ;;
+  restore)  shift; cmd_restore "$@" ;;
+  collect)  shift; cmd_collect "$@" ;;
+  compare)  shift; cmd_compare "$@" ;;
+  virtdiff) shift; cmd_virtdiff "$@" ;;
+  down)     shift; cmd_down "$@" ;;
+  *) sed -n '2,30p' "$0"; exit 1 ;;
+esac

labsim/ipv6-ha-evidence/V0-baseline/state.txt

@@ -0,0 +1,43 @@
+=== 2026-09-06T14:25:25+01:00 ===
+--- HE endpoint ---
+  HE address : 192.0.2.10/32
+  he-sim     : he-sim: ipv6/ip remote 198.51.100.137 local 192.0.2.10 ttl 64 6rd-prefix 2002::/16
+  he-sim v6  : 2001:db8:1f1c:f6::1/64
+  API        : running
+  API bound  : nohost
+  API calls  : 4
+  route back : 198.51.100.0/24 via 192.168.122.63 dev eth1 
+--- 172.31.1.252 ---
+vip=172.31.1.1 holds_vip=no wan_disabled=yes wan_up=no ppp_up=no ppp_active=no may_dial=no lease_age=- dropin=yes role=backup tun=DOWN radvd=inactive
+inactive
+tun0@NONE        DOWN           203.0.113.108 <POINTOPOINT,NOARP> 
+tun0: ipv6/ip remote 192.0.2.10 local 203.0.113.108 ttl 64 tos inherit 6rd-prefix 2002::/16
+inactive
+Sep 05 23:27:45 apitest vrrp-wan[13361]: bond0.53 enable commit took 5s
+Sep 05 23:29:01 apitest vrrp-wan[16369]: GUARD: lease stale (200s > 75s; is vrrp-wan-reconcile.timer running?) -- hanging up pppoe0
+Sep 05 23:29:27 apitest vrrp-wan[17398]: MASTER: dialling pppoe0
+Sep 05 23:29:57 apitest vrrp-wan[18610]: MASTER: dialling pppoe0
+-- Boot 6efc3c9ba47f455e9668454ee6c2fc37 --
+Sep 05 23:34:48 apitest vrrp-wan[6266]: MASTER: dialling pppoe0
+Sep 05 23:34:49 apitest vrrp-wan[6422]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:34:54 apitest vrrp-wan[7130]: bond0.53 enable commit took 5s
+-- Boot 866611afd7c542d4bf8c5117978dcd4a --
+Sep 06 13:21:54 apitest vrrp-wan[544215]: not MASTER: stopping radvd (deprecates the v6 gateway)
+Sep 06 13:21:54 apitest vrrp-wan[544221]: not MASTER: bringing tun0 down
+Sep 06 13:22:01 apitest he-tunnel-follow[544377]: role is now backup
+--- 172.31.1.253 ---
+vip=172.31.1.1 holds_vip=yes wan_disabled=no wan_up=yes ppp_up=yes ppp_active=yes may_dial=yes lease_age=25 dropin=yes role=master tun=UNKNOWN radvd=active
+tun0@NONE        UNKNOWN        198.51.100.137 <POINTOPOINT,NOARP,UP,LOWER_UP> 
+tun0: ipv6/ip remote 192.0.2.10 local 198.51.100.137 ttl 64 tos inherit 6rd-prefix 2002::/16
+default nhid 111 via 2001:db8:1f1c:f6::1 dev tun0 proto static metric 20 pref medium
+active
+Sep 06 09:29:21 vyos vrrp-wan[422441]: MASTER with bond0.53 disabled -> enabling
+Sep 06 09:29:25 vyos vrrp-wan[423516]: bond0.53 enable commit took 4s
+Sep 06 13:22:01 vyos he-tunnel-follow[593096]: role is now master
+Sep 06 13:22:01 vyos he-tunnel-follow[593109]: change seen (203.0.113.108 -> 198.51.100.137) but waiting for stability (1/2)
+Sep 06 13:23:01 vyos he-tunnel-follow[594799]: HE endpoint set to 198.51.100.137 (good 198.51.100.137)
+Sep 06 13:23:01 vyos he-tunnel-follow[594805]: moved tun0 to pppoe0: src 203.0.113.108 -> 198.51.100.137, mtu 1480 -> 1472
+Sep 06 13:24:02 vyos he-tunnel-follow[595700]: in sync: tun0 via pppoe0 src 198.51.100.137 mtu 1472
+Sep 06 13:24:26 vyos he-tunnel-follow[595886]: in sync: tun0 via pppoe0 src 198.51.100.137 mtu 1472
+Sep 06 13:24:26 vyos he-tunnel-follow[595904]: in sync: tun0 via pppoe0 src 198.51.100.137 mtu 1472
+Sep 06 13:25:01 vyos he-tunnel-follow[596311]: in sync: tun0 via pppoe0 src 198.51.100.137 mtu 1472

labsim/ipv6-ha-evidence/mechanism-2026-09-06.txt

@@ -0,0 +1,23 @@
+=== mechanism evidence, labsim, 2026-09-06T14:28:11+01:00 ===
+--- 172.31.1.252 ---
+vip=172.31.1.1 holds_vip=no wan_disabled=yes wan_up=no ppp_up=no ppp_active=no may_dial=no lease_age=- dropin=yes role=backup tun=DOWN radvd=inactive
+inactive
+tun0@NONE        DOWN           203.0.113.108 <POINTOPOINT,NOARP> 
+inactive
+Sep 06 13:22:01 apitest he-tunnel-follow[544377]: role is now backup
+--- 172.31.1.253 ---
+vip=172.31.1.1 holds_vip=yes wan_disabled=no wan_up=yes ppp_up=yes ppp_active=yes may_dial=yes lease_age=26 dropin=yes role=master tun=UNKNOWN radvd=active
+tun0@NONE        UNKNOWN        198.51.100.137 <POINTOPOINT,NOARP,UP,LOWER_UP> 
+active
+Sep 06 13:25:01 vyos he-tunnel-follow[596311]: in sync: tun0 via pppoe0 src 198.51.100.137 mtu 1472
+Sep 06 13:26:01 vyos he-tunnel-follow[598274]: in sync: tun0 via pppoe0 src 198.51.100.137 mtu 1472
+Sep 06 13:27:01 vyos he-tunnel-follow[599393]: in sync: tun0 via pppoe0 src 198.51.100.137 mtu 1472
+Sep 06 13:28:01 vyos he-tunnel-follow[600596]: in sync: tun0 via pppoe0 src 198.51.100.137 mtu 1472
+--- HE endpoint ---
+  HE address : 192.0.2.10/32
+  he-sim     : he-sim: ipv6/ip remote 198.51.100.137 local 192.0.2.10 ttl 64 6rd-prefix 2002::/16
+  he-sim v6  : 2001:db8:1f1c:f6::1/64
+  API        : running
+  API bound  : nohost
+  API calls  : 5
+  route back : 198.51.100.0/24 via 192.168.122.63 dev eth1 

labsim/k8s-up.sh

@@ -0,0 +1,266 @@
+#!/bin/bash
+# A real Kubernetes cluster inside labsim, on the OVS fabric, for rehearsing
+# Cilium <-> VyOS BGP before it goes near the production routers.
+#
+# Why VMs and not k3d: the thing under test is eBGP between Cilium and VyOS
+# across the switch fabric — nodes on VLAN 2, peering with the router's bond0.2
+# leg, directly connected. k3d would put the nodes on a container bridge, which
+# is a different L2 path and would prove something else. (It also needs Docker;
+# this host has podman.)
+#
+# Why not the existing micro VMs: they are Alpine with 256 MB and 1 vCPU. k3s
+# plus Cilium needs an order of magnitude more, and a glibc distro with a stock
+# kernel that Cilium's eBPF probes are actually tested against.
+#
+# Three nodes, not two: ECMP is only meaningfully tested if a node can be
+# drained and MORE THAN ONE path survives.
+#
+# Layout (mirrors production's shape, not its addresses):
+#   labsim-k8s1   172.31.2.11   k3s server
+#   labsim-k8s2   172.31.2.12   agent
+#   labsim-k8s3   172.31.2.13   agent
+#   gateway       172.31.2.1    the VRRP VIP of the router pair under test
+#   BGP peers     172.31.2.252 / .253   the routers' real per-box addresses
+#
+# Idempotent: re-running only creates what is missing.
+#
+# Usage:
+#   ./k8s-up.sh              create/start the cluster
+#   ./k8s-up.sh --kubeconfig fetch kubeconfig to ./labsim-k8s.kubeconfig
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+source "$SCRIPT_DIR/lib.sh"
+source "$SCRIPT_DIR/ovs.sh"
+
+# --- knobs ----------------------------------------------------------------
+K8S_VLAN="${K8S_VLAN:-2}"
+K8S_PREFIX="${K8S_PREFIX:-172.31.2}"
+K8S_NODES="${K8S_NODES:-3}"
+K8S_FIRST_OCTET="${K8S_FIRST_OCTET:-11}"
+# Dual-stack, mirroring production's shape (not its addresses). VLAN 2 v6 is a
+# ULA so nothing here can leak into the real HE /48; node fd00:2::1x matches the
+# BGP peers in sim-net-config.py (K8S_NODES_V6). cluster/service v6 are ULAs too;
+# the LB pool fd61:1e00::/64 is what Cilium advertises (SERVICE_CIDR_V6 there).
+K8S_PREFIX_V6="${K8S_PREFIX_V6:-fd00:2}"        # nodes fd00:2::11/12/13, router ::252/::253
+K8S_ROUTER_V6="${K8S_ROUTER_V6:-fd00:2::252}"   # v6 next-hop (primary router bond0.2)
+CLUSTER_CIDR_V6="${CLUSTER_CIDR_V6:-fd00:42::/56}"
+SERVICE_CIDR_V6="${SERVICE_CIDR_V6:-fd00:43::/112}"
+K8S_MEM="${K8S_MEM:-4096}"          # MB — k3s + cilium + a workload
+K8S_CPUS="${K8S_CPUS:-2}"
+K8S_DISK_GB="${K8S_DISK_GB:-12}"
+K8S_TOKEN="${K8S_TOKEN:-labsim-k3s-token}"
+
+# Debian rather than Alpine: glibc, a stock kernel, and cloud-init that applies
+# network-config properly (the Alpine base in this sim notably does not).
+DEB_URL="${DEB_URL:-https://cloud.debian.org/images/cloud/trixie/latest/debian-13-genericcloud-amd64.qcow2}"
+DEB_BASE="${DEB_BASE:-$IMG_DIR/debian-13-genericcloud-amd64.qcow2}"
+
+# Same version production runs, so CRD shapes and chart flags transfer exactly.
+CILIUM_VERSION="${CILIUM_VERSION:-1.19.1}"
+
+node_name() { echo "labsim-k8s$1"; }
+node_ip()   { echo "${K8S_PREFIX}.$((K8S_FIRST_OCTET + $1 - 1))"; }
+node_ip6()  { echo "${K8S_PREFIX_V6}::$((K8S_FIRST_OCTET + $1 - 1))"; }
+
+# --- base image -----------------------------------------------------------
+ensure_base_image() {
+  if [ -f "$DEB_BASE" ]; then
+    log "base image present: $(basename "$DEB_BASE")"
+    return
+  fi
+  log "fetching Debian cloud image (~330 MB) -> $DEB_BASE"
+  sudo mkdir -p "$IMG_DIR"
+  # .tmp + mv so an interrupted download never leaves a half image that later
+  # runs treat as valid.
+  sudo curl -fsSL --retry 3 -o "${DEB_BASE}.tmp" "$DEB_URL" \
+    || die "could not fetch $DEB_URL"
+  sudo mv "${DEB_BASE}.tmp" "$DEB_BASE"
+  log "base image ready"
+}
+
+# --- cloud-init -----------------------------------------------------------
+# The server node writes the join token; agents wait for the API to answer
+# before joining, because cloud-init ordering across VMs is not guaranteed and
+# a failed join leaves an agent that never retries.
+build_k8s_seed() {
+  local iso="$1" vm="$2" ip="$3" role="$4" server_ip="$5" pubkey="$6" ip6="$7" server_ip6="$8"
+  local tmp; tmp="$(mktemp -d)"
+
+  cat > "$tmp/meta-data" <<EOF
+instance-id: $vm
+local-hostname: $vm
+EOF
+
+  cat > "$tmp/network-config" <<EOF
+version: 2
+ethernets:
+  enp1s0:
+    match:
+      name: "en*"
+    addresses: [$ip/24, $ip6/64]
+    routes:
+      - to: default
+        via: ${K8S_PREFIX}.1
+    nameservers:
+      addresses: [8.8.8.8, 1.1.1.1]
+EOF
+
+  local k3s_exec
+  if [ "$role" = "server" ]; then
+    # flannel/servicelb/traefik off: Cilium is the CNI under test, and k3s's
+    # own ServiceLB would fight Cilium for LoadBalancer addresses. Dual-stack:
+    # both families in cluster-cidr/service-cidr and a dual node-ip, mirroring
+    # production. Pod IPs come from Cilium cluster-pool (node.spec.podCIDRs is
+    # immutable), so cluster-cidr v6 just marks the cluster dual-stack.
+    k3s_exec="server --flannel-backend=none --disable-network-policy --disable=servicelb --disable=traefik --node-ip=$ip,$ip6 --tls-san=$ip --cluster-cidr=10.42.0.0/16,${CLUSTER_CIDR_V6} --service-cidr=10.43.0.0/16,${SERVICE_CIDR_V6} --cluster-init"
+  else
+    k3s_exec="agent --server https://${server_ip}:6443 --node-ip=$ip,$ip6"
+  fi
+
+  cat > "$tmp/user-data" <<EOF
+#cloud-config
+hostname: $vm
+fqdn: $vm
+users:
+  - name: debian
+    groups: [sudo]
+    shell: /bin/bash
+    sudo: ["ALL=(ALL) NOPASSWD:ALL"]
+    lock_passwd: false
+    plain_text_passwd: labsim
+    ssh_authorized_keys:
+      - $pubkey
+ssh_pwauth: true
+disable_root: false
+ssh_authorized_keys:
+  - $pubkey
+
+package_update: true
+packages: [curl, jq, iproute2, tcpdump, bird2]
+
+write_files:
+  # Cilium replaces kube-proxy and needs these; Debian cloud images ship
+  # neither loaded nor persisted.
+  - path: /etc/modules-load.d/cilium.conf
+    content: |
+      br_netfilter
+      overlay
+  - path: /etc/sysctl.d/99-k8s.conf
+    content: |
+      net.ipv4.ip_forward = 1
+      net.bridge.bridge-nf-call-iptables = 1
+
+runcmd:
+  - [ modprobe, br_netfilter ]
+  - [ modprobe, overlay ]
+  - [ sysctl, --system ]
+  - |
+    # Wait for the server's API before an agent tries to join. Without this the
+    # agent fails once and the unit backs off for minutes.
+    if [ "$role" != "server" ]; then
+      for i in \$(seq 1 60); do
+        curl -sk --max-time 3 https://${server_ip}:6443/ping >/dev/null 2>&1 && break
+        sleep 5
+      done
+    fi
+  - |
+    curl -sfL https://get.k3s.io | \
+      INSTALL_K3S_EXEC="$k3s_exec" \
+      K3S_TOKEN="$K8S_TOKEN" \
+      sh -
+EOF
+
+  sudo mkdir -p "$(dirname "$iso")"
+  sudo genisoimage -quiet -output "$iso" -volid cidata -joliet -rock \
+    "$tmp/user-data" "$tmp/meta-data" "$tmp/network-config"
+  rm -rf "$tmp"
+}
+
+# --- VM creation ----------------------------------------------------------
+create_node() {
+  local n="$1" pubkey="$2"
+  local vm; vm="$(node_name "$n")"
+  local ip; ip="$(node_ip "$n")"
+  local ip6; ip6="$(node_ip6 "$n")"
+  local role="agent"; [ "$n" -eq 1 ] && role="server"
+  local server_ip; server_ip="$(node_ip 1)"
+  local server_ip6; server_ip6="$(node_ip6 1)"
+
+  if virsh_q dominfo "$vm" >/dev/null 2>&1; then
+    local state; state="$(virsh_q domstate "$vm" 2>/dev/null | head -1 | tr -d '\n')"
+    if [ "$state" = "running" ]; then
+      log "$vm already running ($ip, $role)"
+    else
+      log "$vm exists but is $state — starting"
+      virsh_q start "$vm" >/dev/null
+    fi
+    return
+  fi
+
+  local disk="$IMG_DIR/${vm}.qcow2"
+  local seed="$IMG_DIR/${vm}-seed.iso"
+
+  log "creating $vm ($ip, $role, ${K8S_MEM}MB/${K8S_CPUS}cpu)"
+  sudo qemu-img create -q -f qcow2 -F qcow2 -b "$DEB_BASE" "$disk" "${K8S_DISK_GB}G" >/dev/null
+  build_k8s_seed "$seed" "$vm" "$ip" "$role" "$server_ip" "$pubkey" "$ip6" "$server_ip6"
+
+  # Access port on the k8s VLAN — same broadcast domain as the routers'
+  # bond0.2 leg, so BGP peering is directly connected exactly as in production.
+  sudo virt-install --connect "$LIBVIRT_URI" --name "$vm" \
+    --memory "$K8S_MEM" --vcpus "$K8S_CPUS" \
+    --disk "path=$disk,format=qcow2,bus=virtio" \
+    --disk "path=$seed,device=cdrom" \
+    --network "network=$OVS_NET,portgroup=vlan${K8S_VLAN},model=virtio" \
+    --os-variant debian12 \
+    --graphics none --noautoconsole --import >/dev/null
+}
+
+fetch_kubeconfig() {
+  local server_ip; server_ip="$(node_ip 1)"
+  local out="$SCRIPT_DIR/labsim-k8s.kubeconfig"
+  log "fetching kubeconfig from $server_ip"
+  ssh -o StrictHostKeyChecking=no -o ConnectTimeout=10 \
+      "debian@${server_ip}" "sudo cat /etc/rancher/k3s/k3s.yaml" \
+    | sed "s|127.0.0.1|${server_ip}|" > "$out"
+  chmod 600 "$out"
+  log "wrote $out"
+  log "use: KUBECONFIG=$out kubectl get nodes"
+}
+
+main() {
+  if [ "${1:-}" = "--kubeconfig" ]; then
+    fetch_kubeconfig
+    return
+  fi
+
+  require_tools
+  command -v genisoimage >/dev/null || die "genisoimage missing (dnf install genisoimage)"
+
+  local pubkey; pubkey="$(find_ssh_pubkey)"
+  log "using SSH key: ${pubkey%% *} ...${pubkey##* }"
+
+  ensure_base_image
+
+  # Select EVERY VLAN, not just the k8s one. ovs_up re-defines the libvirt
+  # network from SELECTED, so narrowing it here silently drops the portgroups
+  # for every other VLAN -- running VMs keep working (their taps are already
+  # attached) and nothing complains until the next VM cannot be attached.
+  # Observed: this deleted vlan1/3/9/10/200/51/53 and only surfaced when the
+  # ISP VMs needed vlan51 and vlan53.
+  selected_vlans
+  log "ensuring OVS fabric (all VLANs, so no portgroup is dropped)"
+  ovs_up
+
+  for n in $(seq 1 "$K8S_NODES"); do
+    create_node "$n" "$pubkey"
+  done
+
+  echo
+  log "nodes created. k3s installs on first boot (a few minutes)."
+  log "watch:   ssh debian@$(node_ip 1) 'sudo systemctl status k3s'"
+  log "then:    $0 --kubeconfig"
+  log "then install Cilium $CILIUM_VERSION and the BGP resources (see README)."
+}
+
+main "$@"

labsim/labsim-dhcp-test.sh

@@ -0,0 +1,219 @@
+#!/bin/bash
+# Prove that VyOS hands each device the address UniFi reserved for it.
+#
+# The question this answers is narrow and important: 30 of the 31 UniFi
+# reservations sit INSIDE the DHCP pool (LoT's pool is 10.0.0.11-10.0.1.254 and
+# only 10.0.0.2 falls outside it). UniFi's dhcpd tolerates that. VyOS uses kea,
+# and whether kea honours in-pool host reservations decides whether the cutover
+# silently renumbers 30 devices. That is not something to predict.
+#
+# Method: boot throwaway VMs whose MAC is a REAL production MAC, on the sim
+# VLAN, and check the address they are given. MACs are the one piece of
+# production config that transplants verbatim -- the subnet is rewritten, the
+# MAC is not -- which is what makes this a real test rather than a rehearsal.
+#
+# Safe: the ovs-labsim bridge contains only internal ports and VM taps, with no
+# physical NIC, so a production MAC here cannot reach or confuse the real LAN.
+# Verified with `ovs-vsctl show` before this script was written.
+#
+#   ./labsim-dhcp-test.sh              run the standard cases
+#   ./labsim-dhcp-test.sh --keep       leave the VMs up for inspection
+#   ./labsim-dhcp-test.sh --clean      just remove any leftover test VMs
+set -uo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+source "$SCRIPT_DIR/lib.sh"
+
+ROUTER_IP="${ROUTER_IP:-172.31.1.1}"
+ROUTER_PW="${ROUTER_PW:-vyos}"
+TEST_VLAN="${TEST_VLAN:-10}"
+BOOT_WAIT="${BOOT_WAIT:-150}"
+TAG="labsim-dhcptest"
+
+# mac|expected|why. "POOL" means: must get an address from the pool and must
+# NOT get any reserved address -- the negative case that stops a pass from
+# meaning merely "DHCP works".
+CASES=(
+  "f8:0d:ac:90:65:c6|172.31.10.46|printer1 - reservation inside the pool"
+  "1c:69:20:7f:bc:77|172.31.11.67|sonoff-matter - in-pool AND across the /23 boundary"
+  "34:e1:d1:80:29:ce|172.31.10.2|Hubitat - the one reservation OUTSIDE the pool"
+  "52:54:00:ab:cd:ef|POOL|unreserved MAC - must get a pool address, not a reserved one"
+)
+
+vm_of() { echo "${TAG}-$(echo "$1" | tr -d ':')"; }
+
+cleanup_vms() {
+  local n=0
+  while read -r vm; do
+    [ -z "$vm" ] && continue
+    virsh_q destroy "$vm" >/dev/null 2>&1
+    virsh_q undefine "$vm" --remove-all-storage >/dev/null 2>&1
+    n=$((n + 1))
+  done < <(virsh_q list --all --name 2>/dev/null | grep "^${TAG}-" || true)
+  [ "$n" -gt 0 ] && log "removed $n test VM(s)"
+  sudo rm -f "$IMG_DIR/${TAG}-"*.qcow2 "$IMG_DIR/${TAG}-"*-seed.iso 2>/dev/null
+  return 0
+}
+
+# A seed that asks for DHCP instead of taking a static address. Alpine's
+# cloud-init ignores network-config here (verified previously and documented in
+# README), so /etc/network/interfaces is what actually takes effect.
+build_dhcp_seed() {
+  local iso="$1" vm="$2" pubkey="$3"
+  local tmp; tmp="$(mktemp -d)"
+  cat > "$tmp/meta-data" <<EOF
+instance-id: $vm
+local-hostname: $vm
+EOF
+  cat > "$tmp/user-data" <<EOF
+#cloud-config
+hostname: $vm
+users:
+  - name: alpine
+    shell: /bin/ash
+    lock_passwd: false
+    plain_text_passwd: labsim
+    ssh_authorized_keys:
+      - $pubkey
+ssh_authorized_keys:
+  - $pubkey
+disable_root: false
+chpasswd:
+  list: |
+    root:labsim
+  expire: false
+write_files:
+  - path: /etc/network/interfaces
+    content: |
+      auto lo
+      iface lo inet loopback
+      auto eth0
+      iface eth0 inet dhcp
+runcmd:
+  - [ sh, -c, "ifdown eth0 2>/dev/null; ifup eth0 || udhcpc -i eth0 -q || true" ]
+EOF
+  python3 - "$tmp/user-data" <<'PY' || die "generated user-data is not valid YAML"
+import sys, yaml
+yaml.safe_load(open(sys.argv[1]).read().split("#cloud-config",1)[1])
+PY
+  sudo genisoimage -quiet -output "$iso" -volid cidata -joliet -rock \
+    "$tmp/user-data" "$tmp/meta-data" >/dev/null 2>&1 || die "seed build failed"
+  rm -rf "$tmp"
+}
+
+router() {
+  timeout 30 sshpass -p "$ROUTER_PW" ssh -o StrictHostKeyChecking=no \
+    -o BatchMode=no -o ConnectTimeout=8 "vyos@$ROUTER_IP" "$@" 2>/dev/null
+}
+
+# --- argument handling ----------------------------------------------------
+KEEP=0
+case "${1:-}" in
+  --clean) cleanup_vms; exit 0 ;;
+  --keep)  KEEP=1 ;;
+  "")      ;;
+  *)       die "usage: $0 [--keep|--clean]" ;;
+esac
+
+command -v sshpass >/dev/null || die "sshpass required"
+require_tools
+[ -f "$BASE_IMAGE" ] || die "base image missing: $BASE_IMAGE (run labsim-up.sh first)"
+
+log "checking the router is serving DHCP..."
+subnets=$(router '/opt/vyatta/bin/vyatta-op-cmd-wrapper show configuration commands | grep -c subnet-id')
+maps=$(router '/opt/vyatta/bin/vyatta-op-cmd-wrapper show configuration commands | grep -c "static-mapping .* mac"')
+log "  router has ${subnets:-0} subnets and ${maps:-0} static-mappings"
+[ "${maps:-0}" -gt 0 ] || die "router has no static-mappings -- apply the generated config first"
+
+cleanup_vms
+
+# Flush the lease database first. This is not tidiness -- it is the condition
+# the cutover actually runs under, because kea does not inherit UniFi's leases
+# and starts empty. It also makes the test deterministic: with stale leases
+# present, kea saw the reserved address as held by "another client" (the same
+# MAC but a different client-id from a previous boot) and allocated a dynamic
+# address instead, which produced three misleading results before this existed.
+log "flushing the router's lease database (cutover starts with an empty one)"
+# Every dhcp4-leases.csv* must go, not just the main file: kea's memfile
+# backend keeps lease-file-cleanup rotations (.1/.2) and restores from them on
+# start, so truncating only the primary leaves the old leases intact.
+router 'sudo systemctl stop isc-kea-dhcp4-server;
+        sudo sh -c "rm -f /config/dhcp/dhcp4-leases.csv*";
+        sudo systemctl start isc-kea-dhcp4-server' >/dev/null
+sleep 5
+remaining="$(router '/opt/vyatta/bin/vyatta-op-cmd-wrapper show dhcp server leases' | sed -n '3,$p' | grep -c .)"
+[ "${remaining:-0}" -eq 0 ] || warn "lease table still has ${remaining} row(s) after flush"
+
+SSH_PUB="$(find_ssh_pubkey)"
+sudo mkdir -p "$IMG_DIR"
+
+# --- boot one VM per case -------------------------------------------------
+for c in "${CASES[@]}"; do
+  IFS='|' read -r mac expected why <<<"$c"
+  vm="$(vm_of "$mac")"
+  disk="$IMG_DIR/${vm}.qcow2"; seed="$IMG_DIR/${vm}-seed.iso"
+  log "booting $vm  mac=$mac  ($why)"
+  sudo qemu-img create -q -f qcow2 -F qcow2 -b "$BASE_IMAGE" "$disk" "$VM_DISK" >/dev/null
+  build_dhcp_seed "$seed" "$vm" "$SSH_PUB"
+  sudo virt-install --connect "$LIBVIRT_URI" --name "$vm" \
+    --memory "$VM_MEM" --vcpus "$VM_CPUS" \
+    --disk "path=$disk,format=qcow2,bus=virtio" \
+    --disk "path=$seed,device=cdrom,readonly=on" \
+    --network "network=labsim-ovs,portgroup=vlan${TEST_VLAN},model=virtio,mac=$mac" \
+    --os-variant alpinelinux3.18 --graphics none --noautoconsole --import >/dev/null \
+    || die "virt-install failed for $vm"
+done
+
+log "waiting ${BOOT_WAIT}s for boot + DHCP..."
+sleep "$BOOT_WAIT"
+
+# --- verdict --------------------------------------------------------------
+# The lease table on the router is the authority: it says what the server
+# decided, independent of whether the guest brought the interface up cleanly.
+leases="$(router '/opt/vyatta/bin/vyatta-op-cmd-wrapper show dhcp server leases')"
+echo
+echo "=== router lease table ==="
+echo "$leases"
+echo
+
+reserved_ips="$(cd "$SCRIPT_DIR/../migration" && python3 unifi-to-vyos.py --mode sim 2>/dev/null \
+  | awk '/static-mapping .* ip-address/ {print $NF}')"
+
+pass=0; fail=0
+printf '%-19s %-16s %-16s %s\n' "MAC" "EXPECTED" "GOT" "RESULT"
+for c in "${CASES[@]}"; do
+  IFS='|' read -r mac expected why <<<"$c"
+  # Never guess which lease is "the" lease. Taking the first match is how an
+  # hours-old lease was once reported as the current answer, turning three
+  # failures into apparent passes.
+  matches="$(echo "$leases" | awk -v m="$mac" 'tolower($2) == tolower(m) {print $1}')"
+  n_match="$(echo "$matches" | grep -c . )"
+  if [ "$n_match" -gt 1 ]; then
+    got="AMBIGUOUS($(echo "$matches" | tr '\n' ',' | sed 's/,$//'))"
+  else
+    got="${matches:-<none>}"
+  fi
+  if [ "${got#AMBIGUOUS}" != "$got" ]; then
+    # More than one lease for this MAC means the flush did not take. Any
+    # verdict from here is a guess, so refuse to give one.
+    result="FAIL (multiple leases -- flush did not take)"
+  elif [ "$expected" = "POOL" ]; then
+    if [ "$got" = "<none>" ]; then
+      result="FAIL (no lease at all)"
+    elif echo "$reserved_ips" | grep -qx "$got"; then
+      result="FAIL (got a RESERVED address)"
+    else
+      result="pass"
+    fi
+  else
+    [ "$got" = "$expected" ] && result="pass" || result="FAIL"
+  fi
+  [ "$result" = "pass" ] && pass=$((pass + 1)) || fail=$((fail + 1))
+  printf '%-19s %-16s %-16s %s\n' "$mac" "$expected" "$got" "$result"
+  printf '  %s\n' "$why"
+done
+
+echo
+log "$pass passed, $fail failed"
+[ "$KEEP" -eq 1 ] && log "VMs left running (--keep). Remove with: $0 --clean" || cleanup_vms
+[ "$fail" -eq 0 ] || exit 1

labsim/labsim-dualstack-convert.sh

@@ -0,0 +1,116 @@
+#!/bin/bash
+# Rehearse the k3s single -> dual-stack conversion on the 3-server etcd cluster,
+# the way production Phase 4 will do it: edit each server's config.yaml (rendered
+# by the PRODUCTION generator) to add the second address family, restart ONE
+# server at a time, and watch what happens in between.
+#
+# Answers the questions a single-node lab cannot:
+#   - does quorum survive a rolling config.yaml change across 3 etcd servers?
+#   - what does a MIXED control plane do (one server dual, two still v4-only)?
+#   - does ServiceCIDR pick up the v6 range on the FIRST server's restart, or
+#     only once all three agree?
+#
+# The node-ip v6 must exist on the box before k3s reads it, so each server first
+# gets a ULA on its interface (fd00:2::3x), mirroring how production nodes get a
+# DHCPv6 address before k3s starts.
+#
+#   ./labsim-dualstack-convert.sh baseline   snapshot the v4-only starting state
+#   ./labsim-dualstack-convert.sh convert    roll the conversion, snapshotting each step
+#   ./labsim-dualstack-convert.sh snapshot   print current SC / podCIDRs / quorum
+set -uo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+NET="${NET:-172.31.2}"; FIRST_OCTET="${FIRST_OCTET:-31}"; SERVERS="${SERVERS:-3}"
+TOKEN="${TOKEN:-labsim-etcd-token}"
+RENDER="${RENDER:-$SCRIPT_DIR/../bastion/src/modules/dist/modules/k3s/bin/render-config.js}"
+EVID="${EVID:-$SCRIPT_DIR/dualstack-evidence}"
+
+# Dual-stack target ranges. ULA/v4 -- the mechanism is what's under test, not the
+# addresses; using ULA keeps sim traffic out of the real /48.
+V4_CLUSTER="10.42.0.0/16"; V6_CLUSTER="fd00:42::/56"
+V4_SERVICE="10.43.0.0/16"; V6_SERVICE="fd00:43::/112"   # /112: apiserver caps v6 service ranges
+V6_NODE_PREFIX="fd00:2"                                  # node-ip v6: fd00:2::3x
+
+SSH=(-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -o ConnectTimeout=8 -o BatchMode=yes)
+node_ip()   { echo "${NET}.$((FIRST_OCTET + $1 - 1))"; }
+node_v6()   { echo "${V6_NODE_PREFIX}::$((FIRST_OCTET + $1 - 1))"; }
+node_name() { echo "labsim-etcd$1"; }
+s() { local n="$1"; shift; timeout "${TMO:-25}" ssh "${SSH[@]}" "debian@$(node_ip "$n")" "$@" 2>/dev/null; }
+k() { s 1 "sudo k3s kubectl $*"; }
+log() { printf '\033[36m==>\033[0m %s\n' "$*"; }
+
+snapshot() {
+  # custom-columns, not jsonpath: the jsonpath range/quotes get mangled through
+  # ssh -> sudo -> kubectl and came back empty.
+  echo "  servicecidr :"
+  s 1 'sudo k3s kubectl get servicecidr -o custom-columns=NAME:.metadata.name,CIDRS:.spec.cidrs --no-headers' 2>/dev/null | sed 's/^/    /'
+  echo "  node podCIDRs:"
+  s 1 'sudo k3s kubectl get nodes -o custom-columns=NAME:.metadata.name,PODCIDRS:.spec.podCIDRs --no-headers' 2>/dev/null | sed 's/^/    /'
+  local ready; ready="$(k get nodes --no-headers 2>/dev/null | wc -l)"
+  echo "  nodes registered: $ready ; apiserver: $(k get --raw /readyz >/dev/null 2>&1 && echo ok || echo DOWN)"
+}
+
+# Re-render node n's config.yaml WITH the dual families and write it back.
+convert_node() {
+  local n="$1"
+  local ip; ip="$(node_ip "$n")"; local v6; v6="$(node_v6 "$n")"
+  log "server $n ($ip): add $v6, re-render dual config.yaml, restart k3s"
+
+  # 1. node-ip v6 must exist before k3s reads it.
+  s "$n" "sudo ip -6 addr add ${v6}/64 dev enp1s0 2>/dev/null; ip -6 -br addr show enp1s0 | grep -o '${v6}/64'" | sed 's/^/    addr: /'
+
+  # 2. render the dual config from the PRODUCTION generator, preserving this
+  #    node's role (node 1 cluster-init, else joining server).
+  local extra=""
+  [ "$n" -ne 1 ] && extra="K3S_SERVER_URL=https://$(node_ip 1):6443 K3S_TOKEN=$TOKEN"
+  local cfg
+  cfg="$(env ROLE=infra HOSTNAME="$(node_name "$n")" IP="$ip" TLS_SANS="$ip" \
+      IPV6="$v6" CLUSTER_CIDR="${V4_CLUSTER},${V6_CLUSTER}" SERVICE_CIDR="${V4_SERVICE},${V6_SERVICE}" \
+      $extra node "$RENDER")"
+  # sanity: the render must actually carry both families or the restart is pointless
+  echo "$cfg" | grep -q "$V6_CLUSTER" || { echo "    RENDER MISSING v6 -- aborting"; return 1; }
+
+  # 3. write it back and restart k3s on this one server.
+  printf '%s\n' "$cfg" | s "$n" "sudo tee /etc/rancher/k3s/config.yaml >/dev/null && sudo systemctl restart k3s"
+
+  # 4. wait for THIS server's k3s to come back and the apiserver to answer.
+  local i
+  for i in $(seq 1 30); do
+    [ "$(s "$n" 'sudo systemctl is-active k3s' 2>/dev/null)" = active ] && \
+      s "$n" 'sudo k3s kubectl get --raw /readyz >/dev/null 2>&1' && break
+    sleep 10
+  done
+  echo "    server $n k3s=$(s "$n" 'systemctl is-active k3s')  restarts=$(s "$n" 'systemctl show k3s -p NRestarts --value')"
+}
+
+cmd_baseline() {
+  mkdir -p "$EVID"
+  { echo "=== BASELINE (v4-only) $(date -u +%FT%TZ) ==="; snapshot; } | tee "$EVID/convert-baseline.txt"
+}
+
+cmd_snapshot() { snapshot; }
+
+cmd_convert() {
+  mkdir -p "$EVID"
+  local out="$EVID/convert-run.txt"
+  {
+    echo "=== 3-SERVER DUAL-STACK CONVERSION $(date -u +%FT%TZ) ==="
+    echo "--- before ---"; snapshot
+    local n
+    for n in $(seq 1 "$SERVERS"); do
+      echo; echo "### converting server $n of $SERVERS ###"
+      convert_node "$n" || { echo "convert_node $n failed"; break; }
+      echo "--- state after server $n (MIXED until n=$SERVERS) ---"
+      snapshot
+    done
+    echo; echo "--- FINAL ---"; snapshot
+  } 2>&1 | tee "$out"
+  log "evidence -> $out"
+}
+
+case "${1:-snapshot}" in
+  baseline) cmd_baseline ;;
+  convert)  cmd_convert ;;
+  snapshot) cmd_snapshot ;;
+  *) echo "usage: $0 {baseline|convert|snapshot}" >&2; exit 2 ;;
+esac

labsim/labsim-dualstack-net.sh

@@ -0,0 +1,221 @@
+#!/bin/bash
+# VLAN 2 gets IPv6 in labsim: addresses, router advertisements and a DHCPv6
+# server with per-MAC reservations.
+#
+# This is the rehearsal of the production change (dual-stack plan, phase 2b) and
+# runs the SAME VyOS config, against the sim router pair, so the production
+# apply is a repeat rather than a first attempt.
+#
+# WHY DHCPv6 AND NOT SLAAC. The cluster needs each node's IPv6 to be knowable in
+# advance and stable: k3s resolves node-ip once at start-up, and a node's
+# identity cannot be allowed to change under it. The estate already answers that
+# question for IPv4 with kea reservations keyed on MAC, so IPv6 answers it the
+# same way and stays one source of truth.
+#
+# DHCPv6 normally keys on DUID, not MAC -- a DUID is generated by the client and
+# is not derivable from its MAC, which would have meant a second, client-owned
+# source of truth. VyOS's static-mapping accepts `mac` as well as `duid`
+# (verified on the sim: the node.tag directory offers duid, mac, ipv6-address,
+# ipv6-prefix), so the reservation can key on the same MAC the v4 one does.
+#
+# The RA carries managed-flag WITH no-autonomous-flag. That combination is what
+# makes the node's address unambiguous: managed sends it to DHCPv6, and
+# non-autonomous stops it also forming a SLAAC address from the same prefix.
+# Leave autonomous on and every node has two global addresses, only one of which
+# anybody reserved -- and whichever labctl happens to find is the one that ends
+# up in node-ip.
+#
+# Both are VALUELESS nodes on this VyOS: `managed-flag` not `managed-flag true`,
+# and `prefix <p> no-autonomous-flag` not `autonomous-flag false`. The value
+# forms are rejected with "is not valid".
+#
+# A FAILED COMMIT DOES NOT MEAN NOTHING CHANGED. VyOS commits node groups
+# independently, so an earlier run of this script left the bond0.2 address and
+# most of the router-advert block applied while `[[service dhcpv6-server]]
+# failed` -- the interface and RA groups had already succeeded. Re-read the
+# config after any failure rather than assuming a clean rollback; that matters
+# more in production than here.
+#
+# TWO THINGS THIS REHEARSAL FOUND, both of which would have bitten production:
+#
+# 1. managed-flag is NECESSARY BUT NOT SUFFICIENT. It only tells the host to use
+#    DHCPv6; the kernel's accept_ra implements SLAAC and nothing else, so a node
+#    with no DHCPv6 *client* running takes no lease at all. The sim's Debian
+#    nodes have neither NetworkManager nor a networkd .network file managing the
+#    interface, so they ended up with a kernel SLAAC address
+#    (2001:db8:187e:2:5054:ff:fe53:731 -- EUI-64 from the MAC) and never asked
+#    for the reserved ::11. Production's Fedora nodes use NetworkManager, which
+#    does run a DHCPv6 client on the managed flag, and the DGX Sparks run
+#    NetworkManager too -- but that must be VERIFIED per node, not assumed. The
+#    k3s module's preflight catches the consequence; the fix is node-side.
+#
+# 2. TURNING AUTONOMOUS OFF DOES NOT RETRACT ADDRESSES ALREADY FORMED. An
+#    earlier partial apply advertised the prefix while autonomous was still on;
+#    the nodes autoconfigured, and adding no-autonomous-flag afterwards left
+#    those addresses in place with a 30-day valid lifetime. So in production,
+#    where VLAN 2 has no IPv6 at all yet, no-autonomous-flag MUST be in the same
+#    commit that first advertises the prefix. Advertise first and tighten later
+#    and every node carries an unreserved EUI-64 address that labctl might pick
+#    up as node-ip.
+#
+#   ./labsim-dualstack-net.sh up       apply to both sim routers
+#   ./labsim-dualstack-net.sh down     remove it again
+#   ./labsim-dualstack-net.sh status   what the routers and nodes think
+#   ./labsim-dualstack-net.sh leases   who has taken an address
+set -uo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+R1="${R1:-172.31.1.252}"   # sim vyos001 -> ::1
+R2="${R2:-172.31.1.253}"   # sim vyos002 -> ::2
+PW="${VYOS_PW:-vyos}"
+
+# Mirrors production's scheme (2001:470:187e:<vlan>::/64) using the
+# documentation prefix, so the shape is rehearsed without putting sim addresses
+# inside a range production announces.
+V6_PREFIX="${V6_PREFIX:-2001:db8:187e:2}"
+LINK_MTU="${LINK_MTU:-1472}"
+# VyOS requires a unique subnet-id per DHCPv6 subnet ("Unique subnet ID not
+# specified for subnet"). Using the VLAN id keeps it self-documenting and
+# collision-free across VLANs.
+VLAN_ID="${VLAN_ID:-2}"
+
+# node -> last hextet. Mirrors the v4 host part (172.31.2.11 -> ::11) so a
+# reservation is readable next to its IPv4 twin.
+NODES=(labsim-k8s1:11 labsim-k8s2:12 labsim-k8s3:13)
+
+SSH=(-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null
+     -o LogLevel=ERROR -o ConnectTimeout=6 -o PreferredAuthentications=password)
+
+log()  { printf '\033[0;36m[ds-net]\033[0m %s\n' "$*"; }
+warn() { printf '\033[1;33m[ds-net]\033[0m %s\n' "$*" >&2; }
+die()  { printf '\033[0;31m[ds-net]\033[0m %s\n' "$*" >&2; exit 1; }
+
+# Drive VyOS from a script FILE, never `vbash -c`. The latter never starts a
+# config session: commit fails to stderr, a helper discards it, and the run
+# reports success having changed nothing. labsim-pppoe-ha-test.sh lost a whole
+# policy matrix to exactly that.
+vyos_apply() {  # host, set-lines on stdin
+    local h="$1" out
+    out="$({ printf '#!/bin/vbash\nsource /opt/vyatta/etc/functions/script-template\nconfigure\n'
+             cat
+             printf 'commit\nsave\nexit\n'
+           } | timeout 120 sshpass -p "$PW" ssh "${SSH[@]}" "vyos@$h" \
+                 'cat > /tmp/ds-net.sh && chmod +x /tmp/ds-net.sh && sudo /tmp/ds-net.sh' 2>&1)"
+    # Read the outcome instead of assuming it. The first version of this script
+    # printed "up" after BOTH routers had failed to commit -- the same shape of
+    # lie this repo has been bitten by before (a matrix reporting coverage it did
+    # not have). vbash exits 0 even when the commit fails, so the text is the
+    # only honest signal.
+    printf '%s\n' "$out" | grep -vE '^\s*$' | sed 's/^/      /' | tail -6
+    if printf '%s' "$out" | grep -qiE 'Commit failed|\[\[.*\]\] failed|Set failed'; then
+        return 1
+    fi
+    return 0
+}
+
+r() { timeout 40 sshpass -p "$PW" ssh "${SSH[@]}" "vyos@$1" "${@:2}" 2>/dev/null; }
+
+mac_of() { sudo virsh domiflist "$1" 2>/dev/null | awk '/52:54/{print $5; exit}'; }
+
+up() {
+    log "collecting node MACs (the reservation key, same as IPv4)"
+    local mappings="" name hextet mac
+    for entry in "${NODES[@]}"; do
+        name="${entry%%:*}"; hextet="${entry##*:}"
+        mac="$(mac_of "$name")"
+        [ -n "$mac" ] || die "no MAC for $name -- is the sim cluster up? (./k8s-up.sh)"
+        log "    $name $mac -> ${V6_PREFIX}::${hextet}"
+        # No trailing newline: `${mappings}` sits on its own line in the heredoc
+        # below and supplies its own. A heredoc terminator is matched LITERALLY
+        # in the source before any expansion, so `${mappings}EOF` is not the
+        # delimiter -- the heredoc ran on, swallowed the rest of this function
+        # and part of down(), and the apply failed with "Invalid command: [EOF]".
+        [ -n "$mappings" ] && mappings+=$'\n'
+        mappings+="set service dhcpv6-server shared-network-name K8S subnet ${V6_PREFIX}::/64 static-mapping ${name} mac '${mac}'
+set service dhcpv6-server shared-network-name K8S subnet ${V6_PREFIX}::/64 static-mapping ${name} ipv6-address '${V6_PREFIX}::${hextet}'"
+    done
+
+    local host pref hextet_self
+    for host in "$R1" "$R2"; do
+        if [ "$host" = "$R1" ]; then pref=high; hextet_self=1; else pref=low; hextet_self=2; fi
+        log "applying to $host (router ${V6_PREFIX}::${hextet_self}, RA preference $pref)"
+        vyos_apply "$host" <<EOF || die "commit failed on $host -- nothing applied there"
+set interfaces bonding bond0 vif 2 address '${V6_PREFIX}::${hextet_self}/64'
+set service router-advert interface bond0.2 prefix ${V6_PREFIX}::/64 valid-lifetime '2592000'
+set service router-advert interface bond0.2 prefix ${V6_PREFIX}::/64 preferred-lifetime '604800'
+set service router-advert interface bond0.2 prefix ${V6_PREFIX}::/64 no-autonomous-flag
+set service router-advert interface bond0.2 managed-flag
+set service router-advert interface bond0.2 link-mtu '${LINK_MTU}'
+set service router-advert interface bond0.2 default-preference '${pref}'
+set service dhcpv6-server shared-network-name K8S subnet ${V6_PREFIX}::/64 subnet-id '${VLAN_ID}'
+${mappings}
+EOF
+    done
+    log "up. Nodes need a DHCPv6 client on their VLAN 2 interface -- see 'status'."
+}
+
+down() {
+    local host
+    for host in "$R1" "$R2"; do
+        log "removing from $host"
+        vyos_apply "$host" <<EOF
+delete service dhcpv6-server
+delete service router-advert interface bond0.2
+delete interfaces bonding bond0 vif 2 address '${V6_PREFIX}::$([ "$host" = "$R1" ] && echo 1 || echo 2)/64'
+EOF
+    done
+    log "down"
+}
+
+status() {
+    local host
+    for host in "$R1" "$R2"; do
+        printf '  --- %s ---\n' "$host"
+        printf '    bond0.2 v6 : %s\n' "$(r "$host" 'ip -6 -br addr show bond0.2 | tr -s " "' || echo '<unreachable>')"
+        printf '    radvd      : %s\n' "$(r "$host" 'systemctl is-active radvd')"
+        # ps|grep, not pgrep: the bracket idiom that stops a self-match gets
+        # mangled through ssh -> vbash quoting and reported "NOT running" for a
+        # daemon that was plainly up.
+        printf '    kea-dhcp6  : %s\n' "$(r "$host" 'c=$(ps -ef | grep -c "[k]ea-dhcp6"); [ "$c" -gt 0 ] && echo running || echo "NOT running"')"
+        # radvd is expected INACTIVE on the backup: vrrp-wan-reconcile's IPv6
+        # plane stops it there so only the master advertises on any VLAN. Not a
+        # fault -- see the step-0 IPv6-follows-master work.
+        printf '    role       : %s\n' "$(r "$host" 'sudo /config/vrrp-wan-reconcile --status 2>/dev/null | grep -o "role=[a-z]*"')"
+    done
+    printf '  --- nodes ---\n'
+    local entry name
+    for entry in "${NODES[@]}"; do
+        name="${entry%%:*}"
+        printf '    %-14s %s\n' "$name" "$(node_v6 "$name")"
+    done
+}
+
+# What global IPv6 does the node actually hold? This is the question labctl asks
+# before it will write node-ip, so ask it the same way.
+node_v6() {
+    # Ask the node, not the hypervisor: virsh domifaddr --source agent needs
+    # qemu-guest-agent, which these images do not carry, and returned nothing
+    # while the nodes plainly had addresses.
+    local name="$1" v4 out
+    case "$name" in *k8s1) v4=172.31.2.11 ;; *k8s2) v4=172.31.2.12 ;; *k8s3) v4=172.31.2.13 ;; *) echo "<unknown>"; return ;; esac
+    out="$(timeout 20 ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null \
+             -o LogLevel=ERROR -o ConnectTimeout=6 -o BatchMode=yes "debian@$v4" \
+             'ip -6 -br addr show scope global 2>/dev/null | tr -s " "' 2>/dev/null)"
+    echo "${out:-<unreachable>}"
+}
+
+leases() {
+    local host
+    for host in "$R1" "$R2"; do
+        printf '  --- %s ---\n' "$host"
+        r "$host" '/opt/vyatta/bin/vyatta-op-cmd-wrapper show dhcpv6-server leases 2>/dev/null || echo "    (no leases command / no leases)"'
+    done
+}
+
+case "${1:-status}" in
+    up)     up ;;
+    down)   down ;;
+    status) status ;;
+    leases) leases ;;
+    *) die "usage: $0 {up|down|status|leases}" ;;
+esac

labsim/labsim-he-endpoint.sh

@@ -0,0 +1,280 @@
+#!/bin/bash
+# Build a fake Hurricane Electric 6in4 endpoint inside labsim.
+#
+# WHY THIS EXISTS
+# The production HE tunnel was never rehearsed. The override that introduced it
+# says so in its own reason text -- "the sim has no public IPv4 and no HE
+# endpoint, so there is nothing to tunnel to" -- and that gap is why IPv6 was
+# the one half of the WAN story with no matrix behind it. Then the WAN became
+# HA and IPv6 did not follow, which nobody caught, because nothing tests it.
+#
+# THE PROBLEM THIS HAD TO SOLVE
+# The sim's two WANs are isolated islands. Verified:
+#
+#     203.0.113.1 from 203.0.113.107 : OK          <- 10 gig analogue
+#     203.0.113.1 from 198.51.100.137 : unreachable
+#     198.51.100.1 from 198.51.100.137 : OK        <- PPPoE analogue
+#     198.51.100.1 from 203.0.113.107 : unreachable
+#
+# A 6in4 tunnel has ONE remote address, and production never changes it -- so an
+# endpoint reachable over only one WAN could not rehearse the case that matters
+# most: the WITHIN-box fall back from the 10 gig to PPPoE, where he-tunnel-follow
+# re-points the tunnel and calls the HE API. That is exactly where the 2026-09-06
+# near-miss lived.
+#
+# So the sim needs a minimal "internet": both ISP boxes already sit on the
+# libvirt default network (192.168.122.0/24) and both forward, so that becomes
+# the backbone, and HE lives on a single address behind it, reachable over
+# either WAN. No new VMs, no new networks.
+#
+#     192.0.2.10  "HE"  -- on isp-dhcp, reached from the PPPoE island via
+#                          192.168.122.136, and directly from the 10 gig island
+#
+# EVERYTHING HERE IS KERNEL-LEVEL, not VyOS config. The ISP boxes are scaffold,
+# not the thing under test: `ip` commands leave no config to drift, no commit to
+# fail, and a reboot cleans up. The ROUTER side is deliberately the opposite --
+# it goes through real VyOS config, because "will VyOS commit a tunnel whose
+# source-address does not exist on this box?" is one of the questions.
+#
+#   ./labsim-he-endpoint.sh up        build it
+#   ./labsim-he-endpoint.sh down      tear it down
+#   ./labsim-he-endpoint.sh status    what is live
+#   ./labsim-he-endpoint.sh calls     how many times the HE API was called
+#   ./labsim-he-endpoint.sh point IP  point the endpoint by hand (sim bookkeeping)
+set -uo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+DHCP_ISP="${DHCP_ISP:-192.168.122.136}"   # owns the 10 gig segment, hosts "HE"
+PPPOE_ISP="${PPPOE_ISP:-192.168.122.63}"  # owns the PPPoE segment
+PW="${VYOS_PW:-vyos}"
+
+# TEST-NET-1 for the endpoint, and the documentation prefix for v6. Production
+# uses 2001:470:187e::/48 from HE; the sim mirrors its SHAPE
+# (2001:db8:187e:<vlan>::/64) so the scheme is exercised, not just the tunnel.
+HE_ADDR="${HE_ADDR:-192.0.2.10}"
+HE_LINK6="${HE_LINK6:-2001:db8:1f1c:f6::1}"   # HE side of the tunnel /64
+RT_LINK6="${RT_LINK6:-2001:db8:1f1c:f6::2}"   # router side
+SITE6="${SITE6:-2001:db8:187e::/48}"          # routed to the router side
+TENGIG_NET="${TENGIG_NET:-203.0.113.0/24}"
+# Any valid address that will never be a router WAN -- see the tunnel creation
+# below for why this cannot be 0.0.0.0.
+PLACEHOLDER_REMOTE="${PLACEHOLDER_REMOTE:-203.0.113.1}"
+PPPOE_NET="${PPPOE_NET:-198.51.100.0/24}"
+
+SSH=(-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null
+     -o LogLevel=ERROR -o ConnectTimeout=6 -o PreferredAuthentications=password)
+dhcp_isp()  { timeout 40 sshpass -p "$PW" ssh "${SSH[@]}" "vyos@$DHCP_ISP" "$@" 2>/dev/null; }
+pppoe_isp() { timeout 40 sshpass -p "$PW" ssh "${SSH[@]}" "vyos@$PPPOE_ISP" "$@" 2>/dev/null; }
+
+log()  { printf '\033[0;36m[he-sim]\033[0m %s\n' "$*"; }
+die()  { printf '\033[0;31m[he-sim]\033[0m %s\n' "$*" >&2; exit 1; }
+
+# --- the stub tunnelbroker API ---------------------------------------------
+# HE's real endpoint is a dyndns-style updater that re-points the tunnel's remote
+# address. This is that, in 40 lines, so the sim can exercise the HE-SIDE half of
+# a failover -- the half production can never safely test.
+#
+# It logs every call to /run/he-sim-api.log, which is what lets the matrix assert
+# the invariant that matters: a ROUTER-level failover must call this ZERO times,
+# because the 10 gig address follows the cloned MAC to the other box unchanged.
+API_PY='
+import http.server, subprocess, urllib.parse, datetime, sys, re
+
+TUN  = "he-sim"
+LOCAL    = sys.argv[1] if len(sys.argv) > 1 else "192.0.2.10"
+V6_LOCAL = sys.argv[2] if len(sys.argv) > 2 else "2001:db8:1f1c:f6::1/64"
+V6_PEER  = sys.argv[3] if len(sys.argv) > 3 else "2001:db8:1f1c:f6::2"
+SITE6    = sys.argv[4] if len(sys.argv) > 4 else "2001:db8:187e::/48"
+LOG  = "/run/he-sim-api.log"
+
+def note(msg):
+    with open(LOG, "a") as f:
+        f.write("%s %s\n" % (datetime.datetime.now().isoformat(timespec="seconds"), msg))
+
+def current_remote():
+    out = subprocess.run(["ip", "tunnel", "show", TUN], capture_output=True, text=True).stdout
+    m = re.search(r"remote ([0-9.]+)", out)
+    return m.group(1) if m else None
+
+class H(http.server.BaseHTTPRequestHandler):
+    def reply(self, body):
+        b = body.encode()
+        self.send_response(200)
+        self.send_header("Content-Type", "text/plain")
+        self.send_header("Content-Length", str(len(b)))
+        self.end_headers()
+        self.wfile.write(b)
+
+    def handle_update(self, qs):
+        q = urllib.parse.parse_qs(qs)
+        ip = (q.get("myip") or [""])[0]
+        if not ip:
+            note("REFUSED no myip"); return self.reply("nohost")
+        cur = current_remote()
+        if cur == ip:
+            note("nochg %s" % ip); return self.reply("nochg %s" % ip)
+        rc = subprocess.run(["ip", "tunnel", "change", TUN, "mode", "sit",
+                             "local", LOCAL, "remote", ip],
+                            capture_output=True, text=True)
+        if rc.returncode != 0:
+            # Recreate rather than report a success we did not achieve. This is
+            # the path that a multipoint tunnel takes; keeping it means a stub
+            # that cannot silently no-op.
+            note("change failed (%s) -- recreating" % rc.stderr.strip())
+            subprocess.run(["ip", "tunnel", "del", TUN], check=False)
+            subprocess.run(["ip", "tunnel", "add", TUN, "mode", "sit",
+                            "local", LOCAL, "remote", ip, "ttl", "64"], check=False)
+            subprocess.run(["ip", "link", "set", TUN, "up", "mtu", "1480"], check=False)
+            subprocess.run(["ip", "-6", "addr", "replace", V6_LOCAL, "dev", TUN], check=False)
+            subprocess.run(["ip", "-6", "route", "replace", SITE6, "via", V6_PEER,
+                            "dev", TUN], check=False)
+        # Verify rather than trust: read the remote back.
+        got = current_remote()
+        if got != ip:
+            note("FAILED to point %s at %s (reads %s)" % (TUN, ip, got))
+            return self.reply("dnserr")
+        note("good %s (was %s)" % (ip, cur))
+        self.reply("good %s" % ip)
+
+    def do_GET(self):
+        u = urllib.parse.urlparse(self.path)
+        if u.path == "/nic/update": self.handle_update(u.query)
+        else: self.reply("badauth")
+
+    def do_POST(self):
+        n = int(self.headers.get("Content-Length") or 0)
+        self.handle_update(self.rfile.read(n).decode())
+
+    def log_message(self, *a): pass
+
+http.server.HTTPServer(("0.0.0.0", 80), H).serve_forever()
+'
+
+up() {
+    log "backbone: teaching each ISP box how to reach the other island"
+    # isp-dhcp owns HE and must be able to answer a router that arrived over
+    # PPPoE, so it needs a route back to that island via the backbone.
+    dhcp_isp "sudo ip route replace $PPPOE_NET via $PPPOE_ISP" \
+        || die "could not add the PPPoE-island route on isp-dhcp"
+    # isp-pppoe must forward its clients' traffic for HE across the backbone.
+    pppoe_isp "sudo ip route replace $HE_ADDR/32 via $DHCP_ISP" \
+        || die "could not add the HE route on isp-pppoe"
+
+    log "HE endpoint: $HE_ADDR on isp-dhcp"
+    # A dummy interface, not a loopback alias: `ip tunnel` wants a real local
+    # address and a dummy is the honest way to have one that is not tied to
+    # either WAN segment -- which is the point, HE is neither.
+    dhcp_isp "sudo modprobe dummy 2>/dev/null;
+              sudo ip link add he-lo type dummy 2>/dev/null;
+              sudo ip link set he-lo up;
+              sudo ip addr replace $HE_ADDR/32 dev he-lo"
+
+    log "6in4 tunnel he-sim: local $HE_ADDR, remote set by the API on demand"
+    # A PLACEHOLDER remote, not 0.0.0.0. A sit tunnel created with `remote any`
+    # is multipoint (6rd-shaped), and `ip tunnel change` then refuses to convert
+    # it to point-to-point -- "add tunnel he-sim failed: Invalid argument". The
+    # API's update silently did nothing, so the stub logged "good", production's
+    # he-tunnel-follow logged success, and the tunnel still pointed nowhere.
+    # Created point-to-point from the start, `change` works.
+    dhcp_isp "sudo ip tunnel del he-sim 2>/dev/null;
+              sudo ip tunnel add he-sim mode sit local $HE_ADDR remote $PLACEHOLDER_REMOTE ttl 64;
+              sudo ip link set he-sim up mtu 1480;
+              sudo ip -6 addr replace $HE_LINK6/64 dev he-sim;
+              sudo ip -6 route replace $SITE6 via $RT_LINK6 dev he-sim;
+              sudo sysctl -qw net.ipv6.conf.all.forwarding=1"
+
+    log "stub tunnelbroker API on $HE_ADDR:80"
+    printf '%s' "$API_PY" | dhcp_isp "cat > /tmp/he-sim-api.py"
+    # Launch from a script FILE, not an inline ssh command. The remote login
+    # shell is vbash, and a multi-line inlined `sudo setsid nohup ... &` through
+    # it silently ran nothing at all: no process, no /run/he-sim-api.out, and a
+    # `pgrep -f he-sim-api.py` status check that reported "running" because the
+    # unbracketed pattern matched its OWN ssh command line. Two self-inflicted
+    # illusions stacked on each other.
+    #
+    # This repo already learned this once -- see isp_session_control() in
+    # labsim-pppoe-ha-test.sh, where driving vbash inline made every iteration
+    # of the T4 matrix test the wrong policy while printing the right one.
+    printf '%s\n' \
+        '#!/bin/sh' \
+        '# started detached so it outlives the ssh session that launched it' \
+        'pkill -f "he-sim-api[.]py" 2>/dev/null' \
+        'rm -f /run/he-sim-api.log /run/he-sim-api.out' \
+        "exec setsid python3 /tmp/he-sim-api.py $HE_ADDR '$HE_LINK6/64' $RT_LINK6 $SITE6 >/run/he-sim-api.out 2>&1 </dev/null &" \
+        | dhcp_isp "cat > /tmp/he-sim-start.sh"
+    dhcp_isp "chmod +x /tmp/he-sim-start.sh && sudo /tmp/he-sim-start.sh" >/dev/null
+    # Poll for the bind rather than sleeping a guessed interval.
+    local i probe=""
+    for i in $(seq 1 10); do
+        sleep 1
+        probe="$(dhcp_isp "curl -sS --max-time 3 'http://$HE_ADDR/nic/update' 2>&1")"
+        [ "$probe" = nohost ] && break
+    done
+    case "$probe" in
+        nohost) log "API answering (returned 'nohost' for a call with no myip -- correct)" ;;
+        *)      die "stub API not answering on $HE_ADDR:80 (got: ${probe:-<nothing>})" ;;
+    esac
+
+    log "up. Router side is NOT configured by this script -- that is real VyOS"
+    log "config and belongs to the matrix; see labsim-ipv6-ha-test.sh --setup."
+}
+
+down() {
+    log "tearing down"
+    dhcp_isp "sudo pkill -f 'he-sim-api[.]py' 2>/dev/null;
+              sudo ip tunnel del he-sim 2>/dev/null;
+              sudo ip link del he-lo 2>/dev/null;
+              sudo ip route del $PPPOE_NET via $PPPOE_ISP 2>/dev/null" >/dev/null
+    pppoe_isp "sudo ip route del $HE_ADDR/32 via $DHCP_ISP 2>/dev/null" >/dev/null
+    log "down"
+}
+
+status() {
+    printf '  HE address : %s\n' "$(dhcp_isp "ip -4 -br addr show he-lo 2>/dev/null | awk '{print \$3}'" || echo '<absent>')"
+    printf '  he-sim     : %s\n' "$(dhcp_isp "ip tunnel show he-sim 2>/dev/null" || echo '<absent>')"
+    printf '  he-sim v6  : %s\n' "$(dhcp_isp "ip -6 -br addr show he-sim 2>/dev/null | awk '{print \$3}'" || echo '-')"
+    # Bracketed so the pattern cannot match the ssh command line carrying it --
+    # unbracketed, this reported "running" while nothing was listening at all.
+    printf '  API        : %s\n' "$(dhcp_isp "pgrep -f 'he-sim-api[.]py' >/dev/null && echo running || echo stopped")"
+    printf '  API bound  : %s\n' "$(dhcp_isp "curl -sS --max-time 3 'http://$HE_ADDR/nic/update' 2>/dev/null" || echo 'NOT ANSWERING')"
+    printf '  API calls  : %s\n' "$(dhcp_isp "grep -c . /run/he-sim-api.log 2>/dev/null" || echo 0)"
+    printf '  route back : %s\n' "$(dhcp_isp "ip route show $PPPOE_NET 2>/dev/null" || echo '<none>')"
+}
+
+# Count of endpoint-CHANGING calls. `nochg` does not count: production's
+# he-tunnel-follow re-sends the same address happily and HE treats it as a
+# no-op, so only a real move is evidence that something re-pointed the tunnel.
+calls() { dhcp_isp "grep -c ' good ' /run/he-sim-api.log 2>/dev/null" | tr -d ' \n'; }
+
+# Point the endpoint at an address WITHOUT going through the API, and without
+# counting as an API call.
+#
+# Needed because rebuilding the sim endpoint resets its remote, while the
+# routers' he-tunnel-follow still reads "in sync" and therefore never re-asserts
+# -- it only calls HE when its own LOCAL source changes, and has no way to learn
+# that the far end drifted. The real HE does not forget, so this is sim
+# bookkeeping, not a behaviour production needs. Keeping it out of the call
+# counter is the point: the matrix asserts on that counter.
+point() {
+    local ip="$1"
+    [ -n "$ip" ] || die "usage: $0 point <ipv4>"
+    dhcp_isp "sudo ip tunnel change he-sim mode sit local $HE_ADDR remote $ip 2>/dev/null \
+              || { sudo ip tunnel del he-sim 2>/dev/null;
+                   sudo ip tunnel add he-sim mode sit local $HE_ADDR remote $ip ttl 64;
+                   sudo ip link set he-sim up mtu 1480;
+                   sudo ip -6 addr replace $HE_LINK6/64 dev he-sim;
+                   sudo ip -6 route replace $SITE6 via $RT_LINK6 dev he-sim; }"
+    local got
+    got="$(dhcp_isp "ip tunnel show he-sim 2>/dev/null | sed -nE 's/.* remote ([0-9.]+).*/\\1/p'" | tr -d ' \n')"
+    [ "$got" = "$ip" ] || die "endpoint still points at ${got:-nothing}, wanted $ip"
+    log "endpoint now points at $ip"
+}
+
+case "${1:-status}" in
+    up)     up ;;
+    down)   down ;;
+    status) status ;;
+    calls)  calls; echo ;;
+    point)  point "${2:-}" ;;
+    *) die "usage: $0 {up|down|status|calls}" ;;
+esac

labsim/labsim-ipv6-ha-test.sh

@@ -0,0 +1,430 @@
+#!/bin/bash
+# Does IPv6 follow VRRP mastership, and does it do so WITHOUT touching HE?
+#
+# The WAN became HA on 2026-09-06 and IPv6 did not follow it. Nothing caught
+# that, because nothing tested it: wan-drill measured IPv4 only, and PPPOE-HA.md
+# recorded "IPv6 stayed up at 15.5ms" from a reading taken outside the failover
+# window. This is the matrix that would have caught it.
+#
+# TWO INVARIANTS, checked independently of any individual test:
+#
+#   1. At most ONE router ever has a live tunnel. An UP tunnel on a box that
+#      does not own the source address is not harmless -- see V4, it is a
+#      BLACKHOLE that will happily attract the v6 default route.
+#   2. A ROUTER-level failover calls the HE API ZERO times. The 10 gig address
+#      is bound to a cloned MAC and follows the VIP to the other box unchanged,
+#      so there is nothing to tell HE. A non-zero count means something
+#      re-pointed the tunnel at a PPPoE address -- which the ISP re-issues on
+#      every dial, so it would be wrong within minutes.
+#
+# KNOWN SIM GAP, 2026-09-06 -- read this before believing a v6_online failure.
+# The MECHANISM is proven here: tun0 up on the master and down on the backup,
+# radvd following mastership, he-tunnel-follow's master guard, its hysteresis,
+# its HE call and the 1480->1472 MTU switch, and VLAN 9 hosts autoconfiguring
+# from the RA (observed: real SLAAC traffic from 2001:db8:187e:9::/64 arriving
+# at the endpoint encapsulated).
+#
+# What is NOT yet proven is the end-to-end v6 DATAPATH, because the sim's
+# "internet" is asymmetric: 6in4 packets from the PPPoE island reach the
+# endpoint with an outer source of 192.168.122.1 -- the libvirt host's NAT --
+# so HE's replies go back to the tunnel remote by a path with no NAT state and
+# are lost. Forward works, return does not.
+#
+# That is a topology fault in the scaffold, not in the thing under test. Fixing
+# it means giving the two ISP islands a real transit path that does not traverse
+# libvirt NAT. Until then, treat v6_online failures as UNPROVEN rather than as
+# evidence the design is wrong -- and do not let that ambiguity leak into
+# production sign-off, which is exactly the mistake wan-drill made by asserting
+# "IPv6 stayed up" from a reading taken outside the window.
+#
+# Requires the fake HE endpoint: ./labsim-he-endpoint.sh up
+#
+#   ./labsim-ipv6-ha-test.sh --setup    configure the router side (once)
+#   ./labsim-ipv6-ha-test.sh --list
+#   ./labsim-ipv6-ha-test.sh V1
+#   ./labsim-ipv6-ha-test.sh --all
+set -uo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+R1="${R1:-172.31.1.252}"; R2="${R2:-172.31.1.253}"
+VIP="${VIP:-172.31.1.1}"
+LAN9="${LAN9:-172.31.9.10}"                  # VLAN 9 client, for RA tests
+HE_ADDR="${HE_ADDR:-192.0.2.10}"
+HE_LINK6="${HE_LINK6:-2001:db8:1f1c:f6::1}"
+RT_LINK6="${RT_LINK6:-2001:db8:1f1c:f6::2}"
+V9_PREFIX="${V9_PREFIX:-2001:db8:187e:9}"
+# Mirrors production: one MAC, one lease, whichever router holds the VIP.
+WAN_MAC="${WAN_MAC:-02:9f:c2:12:9b:4f}"
+PW="${VYOS_PW:-vyos}"; LANPW="${LANPW:-labsim}"
+EVID="$SCRIPT_DIR/ipv6-ha-evidence"
+HE="$SCRIPT_DIR/labsim-he-endpoint.sh"
+
+SSH=(-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null
+     -o LogLevel=ERROR -o ConnectTimeout=6 -o PreferredAuthentications=password)
+r() { timeout 45 sshpass -p "$PW" ssh "${SSH[@]}" "vyos@$1" "${@:2}" 2>/dev/null; }
+# The Alpine LAN VMs do not offer `password` auth -- reusing the routers' option
+# set makes ssh exit 255 before running anything, which reads as "the network is
+# broken". Same trap as lan() in labsim-pppoe-ha-test.sh.
+LAN_SSH=(-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null
+         -o LogLevel=ERROR -o ConnectTimeout=6)
+lan9() { timeout 30 sshpass -p "$LANPW" ssh "${LAN_SSH[@]}" "root@$LAN9" "$@" 2>/dev/null; }
+
+log()  { printf '\033[36m==>\033[0m %s\n' "$*"; }
+pass() { printf '  \033[32mPASS\033[0m %s\n' "$*"; }
+fail() { printf '  \033[31mFAIL\033[0m %s\n' "$*"; FAILED=$((FAILED+1)); }
+warn() { printf '  \033[33mWARN\033[0m %s\n' "$*"; }
+FAILED=0
+
+# --- observations ----------------------------------------------------------
+# A destroyed or unreachable router is emphatically NOT holding the tunnel, but
+# ssh returns an EMPTY string, and `[ "" = 0 ]` is false -- the pppoe matrix hung
+# on exactly this waiting for a dead box to report zero. Default everything to 0.
+tun_state() { local v; v="$(r "$1" "ip -br link show tun0 2>/dev/null | awk '{print \$2}'" | tr -d ' \n')"; echo "${v:-absent}"; }
+tun_src()   { r "$1" 'ip tunnel show tun0 2>/dev/null | sed -nE "s/.* local ([0-9.]+).*/\1/p"' | tr -d ' \n'; }
+# Whichever router currently holds the 10 gig lease -- under the cloned MAC only
+# one ever does. Read rather than assumed: the address changes when the MAC does.
+tengig_addr() { local h a; for h in "$R1" "$R2"; do
+                  a="$(r "$h" 'ip -4 addr show bond0.53 2>/dev/null | sed -nE "s/.*inet ([0-9.]+).*/\1/p"' | tr -d ' \n')"
+                  [ -n "$a" ] && { echo "$a"; return; }
+                done; echo ""; }
+tun_mtu()   { local v; v="$(r "$1" 'cat /sys/class/net/tun0/mtu 2>/dev/null' | tr -d ' \n')"; echo "${v:-0}"; }
+holder()    { for h in "$R1" "$R2"; do
+                [ "$(r "$h" "ip -4 -o addr show | grep -c ' ${VIP}/'" | tr -d ' \n')" != 0 ] \
+                  && { echo "$h"; return; }; done; echo none; }
+# Ask the ROUTER, not a client: a client can be answered by the wrong path.
+v6_online() { [ "$(r "$1" "ping -6 -c1 -W3 $HE_LINK6 >/dev/null 2>&1 && echo y" | tr -d ' \n')" = y ]; }
+radvd_on()  { [ "$(r "$1" 'systemctl is-active radvd 2>/dev/null' | tr -d ' \n')" = active ]; }
+he_calls()  { timeout 60 "$HE" calls | tr -d ' \n'; }
+
+# How many routers have a tunnel that is UP. Invariant 1's numerator.
+tun_holders() { local n=0 h; for h in "$R1" "$R2"; do
+                  case "$(tun_state "$h")" in UP|UNKNOWN) n=$((n+1)) ;; esac
+                done; echo "$n"; }
+
+check_invariants() {
+    local t ok=0
+    t="$(tun_holders)"
+    [ "${t:-0}" -le 1 ] || { fail "INVARIANT: $t routers have tun0 up"; ok=1; }
+    return $ok
+}
+
+save_evidence() {
+    local name="$1"; local d="$EVID/$name"; mkdir -p "$d"
+    { echo "=== $(date -Is) ==="
+      echo "--- HE endpoint ---"; timeout 60 "$HE" status
+      for h in "$R1" "$R2"; do echo "--- $h ---"
+        r "$h" 'sudo /config/vrrp-wan-reconcile --status 2>/dev/null
+                ip -br link show tun0 2>/dev/null; ip tunnel show tun0 2>/dev/null
+                ip -6 route show default; systemctl is-active radvd
+                sudo journalctl -t vrrp-wan -t he-tunnel-follow -n 10 --no-pager'
+      done; } > "$d/state.txt" 2>&1
+    log "evidence -> ipv6-ha-evidence/$name/"
+}
+
+# --- setup ------------------------------------------------------------------
+# Applied through REAL VyOS config, unlike the ISP-side scaffold, because "will
+# VyOS accept this?" is one of the questions being asked.
+vyos_apply() {   # host, then set-lines on stdin
+    local h="$1"
+    { printf '#!/bin/vbash\nsource /opt/vyatta/etc/functions/script-template\nconfigure\n'
+      cat
+      printf 'commit\nsave\nexit\n'
+    } | timeout 90 sshpass -p "$PW" ssh "${SSH[@]}" "vyos@$h" \
+          'cat > /tmp/v6-apply.sh && chmod +x /tmp/v6-apply.sh && sudo /tmp/v6-apply.sh' 2>&1 | tail -3
+    # `vbash -c` never starts a config session and commit fails to stderr, which
+    # a helper like this discards -- the T4 matrix in labsim-pppoe-ha-test.sh ran
+    # its whole policy sweep against the default while printing the mode it
+    # thought it was testing. Always read the value back.
+}
+
+setup() {
+    log "--setup: router-side IPv6, both routers"
+
+    # THE CLONED MAC, first and on its own. Production pins f0:9f:c2:12:9b:4f on
+    # vif 53 so the 10 gig lease follows the VIP and the tunnel source is the
+    # SAME address on either box. The sim never had it -- each router took its
+    # own lease -- so the sim could not reproduce the one property the whole
+    # IPv6-HA design leans on, and invariant 2 would have been untestable here.
+    local h pref v9
+    for h in "$R1" "$R2"; do
+        log "    $h: pinning the cloned WAN MAC $WAN_MAC"
+        vyos_apply "$h" <<EOF
+set interfaces bonding bond0 vif 53 mac '$WAN_MAC'
+EOF
+    done
+
+    # A new MAC means a NEW lease, so the tunnel source cannot be hardcoded --
+    # discover it. Hardcoding the pre-change address here would have configured
+    # every tunnel with a source neither router owns, i.e. the V4 blackhole, on
+    # both boxes, while the matrix reported setup success.
+    local src="" i
+    for i in $(seq 1 30); do
+        src="$(tengig_addr)"; [ -n "$src" ] && break
+        sleep 5
+    done
+    [ -n "$src" ] || { fail "no router took a 10 gig lease after the MAC change -- cannot set a tunnel source"; return 1; }
+    log "    10 gig lease under the cloned MAC: $src"
+
+    # Credentials pointing at the stub. HE_UPDATE_URL is read AFTER the secrets
+    # file is sourced, so putting it here overrides the production default
+    # without the script needing a sim-specific branch.
+    for h in "$R1" "$R2"; do
+        printf 'HE_USER=sim\nHE_UPDATE_KEY=sim\nHE_TUNNEL_ID=1\nHE_UPDATE_URL=http://%s/nic/update\n' "$HE_ADDR" \
+          | timeout 30 sshpass -p "$PW" ssh "${SSH[@]}" "vyos@$h" \
+              'cat > /tmp/he-secrets && sudo install -o root -g vyattacfg -m 0640 /tmp/he-secrets /config/he-secrets' >/dev/null
+    done
+
+    for h in "$R1" "$R2"; do
+        [ "$h" = "$R1" ] && { pref=high; v9=1; } || { pref=low; v9=2; }
+        log "    $h (RA preference $pref, bond0.9 ::${v9})"
+        vyos_apply "$h" <<EOF
+set interfaces tunnel tun0 encapsulation 'sit'
+set interfaces tunnel tun0 source-address '$src'
+set interfaces tunnel tun0 remote '$HE_ADDR'
+set interfaces tunnel tun0 address '$RT_LINK6/64'
+set interfaces tunnel tun0 mtu '1480'
+set protocols static route6 ::/0 next-hop '$HE_LINK6'
+set interfaces bonding bond0 vif 9 address '${V9_PREFIX}::${v9}/64'
+set service router-advert interface bond0.9 prefix ${V9_PREFIX}::/64 preferred-lifetime '604800'
+set service router-advert interface bond0.9 link-mtu '1472'
+set service router-advert interface bond0.9 default-preference '$pref'
+set system task-scheduler task he-tunnel-follow executable path '/config/he-tunnel-follow'
+set system task-scheduler task he-tunnel-follow executable arguments 'run'
+set system task-scheduler task he-tunnel-follow interval '1m'
+EOF
+    done
+    # RA link-mtu is 1472, the PPPoE figure, on BOTH -- deliberately not 1480.
+    # It cannot be reconciled at runtime (it needs a commit, and the tunnel plane
+    # is commit-free on purpose), so advertise the lower of the two paths and be
+    # correct on either WAN. Production pinned 1480 and was wrong whenever the
+    # WAN fell back.
+    log "    setup done -- run V0 to check the baseline"
+}
+
+# --- tests ------------------------------------------------------------------
+V0() {  # baseline
+    log "V0  baseline: the VIP holder owns the tunnel, the backup does not"
+    local h o; h="$(holder)"; o=$([ "$h" = "$R1" ] && echo "$R2" || echo "$R1")
+    [ "$h" = none ] && { fail "no VIP holder"; return; }
+    case "$(tun_state "$h")" in UP|UNKNOWN) pass "master $h has tun0 up" ;;
+        *) fail "master $h tun0 is $(tun_state "$h")" ;; esac
+    case "$(tun_state "$o")" in DOWN|absent) pass "backup $o tun0 is $(tun_state "$o")" ;;
+        *) fail "backup $o tun0 is $(tun_state "$o") -- it should be held down" ;; esac
+    v6_online "$h" && pass "master reaches HE over v6" || fail "master has no IPv6"
+    radvd_on "$h" && pass "master is advertising on VLAN 9" || fail "master radvd not running"
+    radvd_on "$o" && fail "backup is ALSO advertising -- two default routers on VLAN 9" \
+                  || pass "backup is not advertising"
+    check_invariants
+    save_evidence V0-baseline
+}
+
+V1() {  # clean failover: v6 follows, and HE is never called
+    log "V1  clean failover: IPv6 follows, HE API untouched"
+    local from to t0 before after i
+    from="$(holder)"; to=$([ "$from" = "$R1" ] && echo "$R2" || echo "$R1")
+    before="$(he_calls)"
+    log "    master=$from -> expecting $to (HE calls so far: ${before:-0})"
+    t0=$(date +%s)
+    r "$from" 'sudo mkdir -p /run/vrrp-wan && sudo touch /run/vrrp-wan/force-fault'
+    local took=""
+    for i in $(seq 1 36); do
+        sleep 5
+        [ "$(holder)" = "$to" ] && v6_online "$to" && { took=$(( $(date +%s) - t0 )); break; }
+    done
+    [ -n "$took" ] && pass "IPv6 reached $to in ${took}s" \
+                   || fail "IPv6 never followed to $to within 180s"
+    case "$(tun_state "$from")" in DOWN|absent) pass "$from released its tunnel" ;;
+        *) fail "$from still has tun0 $(tun_state "$from") -- blackhole risk" ;; esac
+    after="$(he_calls)"
+    # THE invariant this test exists for.
+    [ "${after:-0}" = "${before:-0}" ] \
+        && pass "HE API not called (${after:-0} total) -- the address followed the MAC" \
+        || fail "HE API called $(( ${after:-0} - ${before:-0} )) time(s) during a ROUTER failover"
+    check_invariants
+    save_evidence V1-clean-failover
+    r "$from" 'sudo rm -f /run/vrrp-wan/force-fault'
+    sleep 40
+}
+
+V2() {  # 10 gig down on the master: HE must be told, exactly once
+    log "V2  10 gig down: he-tunnel-follow re-points the tunnel and tells HE"
+    local h before after mtu i ok=no
+    h="$(holder)"; before="$(he_calls)"
+    local tengig; tengig="$(tengig_addr)"
+    r "$h" 'sudo ip link set bond0.53 down'
+    # he-tunnel-follow runs on a 1m task-scheduler with a 2-tick hysteresis, so
+    # allow well past 2 minutes before calling it a failure.
+    for i in $(seq 1 30); do
+        sleep 10
+        [ "$(tun_src "$h")" != "$tengig" ] && { ok=yes; break; }
+    done
+    [ "$ok" = yes ] && pass "tunnel source moved to $(tun_src "$h") after $((i*10))s" \
+                    || fail "tunnel source never left the 10 gig address"
+    mtu="$(tun_mtu "$h")"
+    [ "$mtu" = 1472 ] && pass "MTU dropped to 1472 for the PPPoE path" \
+                      || fail "MTU is $mtu, want 1472 -- large transfers will hang"
+    after="$(he_calls)"
+    [ "$(( ${after:-0} - ${before:-0} ))" -ge 1 ] \
+        && pass "HE API called $(( ${after:-0} - ${before:-0} )) time(s), as it must be here" \
+        || fail "HE was never told -- it still points at an address this box no longer has"
+    v6_online "$h" && pass "IPv6 still up over PPPoE" || fail "IPv6 down on the PPPoE path"
+    save_evidence V2-tengig-down
+    r "$h" 'sudo ip link set bond0.53 up'
+    sleep 60
+}
+
+V3() {  # a cold backup must not advertise, dial, or blackhole
+    log "V3  cold backup: no tunnel, no RA, no HE call"
+    local h o before after
+    h="$(holder)"; o=$([ "$h" = "$R1" ] && echo "$R2" || echo "$R1")
+    before="$(he_calls)"
+    r "$o" 'sudo systemctl restart vrrp-wan-reconcile.service' >/dev/null
+    sleep 20
+    case "$(tun_state "$o")" in DOWN|absent) pass "backup tunnel stays $(tun_state "$o")" ;;
+        *) fail "backup brought tun0 up while not holding the VIP" ;; esac
+    radvd_on "$o" && fail "backup is advertising on VLAN 9" || pass "backup is silent on VLAN 9"
+    after="$(he_calls)"
+    [ "${after:-0}" = "${before:-0}" ] && pass "backup made no HE call" \
+        || fail "the BACKUP called the HE API -- it would point HE at its own idle line"
+    save_evidence V3-cold-backup
+}
+
+V4() {  # the assumption the production override was built on
+    log "V4  a tunnel whose source-address is absent: what does VyOS actually do?"
+    # The production override says such a tunnel "would simply stay down", and
+    # treats that as the reason it was safe to leave IPv6 single-homed. Measured
+    # on the sim backup 2026-09-06: the commit SUCCEEDS and the link comes up
+    # anyway -- it is a blackhole, not an inert node. That is why the runtime
+    # gate is load-bearing rather than a nicety, exactly like the PPPoE gate.
+    local o h; h="$(holder)"; o=$([ "$h" = "$R1" ] && echo "$R2" || echo "$R1")
+    r "$o" 'sudo ip link set tun0 up' >/dev/null; sleep 3
+    case "$(tun_state "$o")" in
+        UP|UNKNOWN) pass "confirmed: VyOS leaves it UP with no source address (blackhole)" ;;
+        *) warn "this VyOS version keeps it $(tun_state "$o") -- the override's assumption holds here; re-check the production version before relying on it" ;;
+    esac
+    v6_online "$o" && fail "the backup somehow reached HE -- two live tunnels" \
+                   || pass "and it carries nothing, as expected"
+    # Hand it straight back to the reconciler rather than leaving it up.
+    r "$o" 'sudo systemctl restart vrrp-wan-reconcile.service' >/dev/null
+    sleep 15
+    case "$(tun_state "$o")" in DOWN|absent) pass "the reconciler put it back down" ;;
+        *) fail "the reconciler did NOT re-close the gate -- this is the load-bearing bit" ;; esac
+    save_evidence V4-absent-source-address
+}
+
+V5() {  # never two live tunnels, even mid-transition
+    log "V5  both routers momentarily master: never two live tunnels"
+    local from to i worst=0 n
+    from="$(holder)"; to=$([ "$from" = "$R1" ] && echo "$R2" || echo "$R1")
+    r "$from" 'sudo mkdir -p /run/vrrp-wan && sudo touch /run/vrrp-wan/force-fault'
+    # Sample THROUGH the transition rather than at the ends. The interesting
+    # window is the one where both boxes briefly think they are in charge.
+    for i in $(seq 1 24); do
+        n="$(tun_holders)"; [ "${n:-0}" -gt "$worst" ] && worst="$n"
+        sleep 5
+    done
+    [ "$worst" -le 1 ] && pass "at most $worst live tunnel throughout the transition" \
+                       || fail "saw $worst live tunnels at once -- HE would receive two claimants"
+    r "$from" 'sudo rm -f /run/vrrp-wan/force-fault'
+    save_evidence V5-transition-invariant
+    sleep 40
+}
+
+V6() {  # RA deprecation: does a VLAN 9 host drop the dead gateway?
+    log "V6  RA deprecation: the client must stop using a demoted router"
+    local h before
+    h="$(holder)"
+    before="$(lan9 'ip -6 route show default 2>/dev/null | head -1')"
+    if [ -z "$before" ]; then
+        warn "VLAN 9 client has no IPv6 default route -- SLAAC may not have run; skipping"
+        return
+    fi
+    log "    client default was: $before"
+    r "$h" 'sudo mkdir -p /run/vrrp-wan && sudo touch /run/vrrp-wan/force-fault'
+    sleep 45
+    local after; after="$(lan9 'ip -6 route show default 2>/dev/null | head -1')"
+    log "    client default now: ${after:-<none>}"
+    # radvd emits a final RA with router-lifetime 0 on a graceful stop. Either
+    # the client moved to the new master or it dropped the route entirely; both
+    # are correct. Still pointing at the demoted box is not.
+    if [ "$after" = "$before" ]; then
+        fail "client still points at the demoted router -- the farewell RA did not land"
+    else
+        pass "client stopped using the demoted router"
+    fi
+    r "$h" 'sudo rm -f /run/vrrp-wan/force-fault'
+    save_evidence V6-ra-deprecation
+    sleep 40
+}
+
+V7() {  # replay the 2026-09-06 near-miss, but slowly
+    log "V7  slow WAN restore: does the hysteresis still hold?"
+    # On 2026-09-06 vif53-pin-boot-disable bounced the 10 gig, he-tunnel-follow
+    # ticked once and saw the PPPoE address, and vyos-failover restored the 10
+    # gig 22 SECONDS before the second tick would have pushed HE at an address
+    # Vodafone reissues on every dial. 22s of margin is not a safety property.
+    # Here the restore is deliberately slower than the hysteresis window.
+    local h before after tengig
+    h="$(holder)"; before="$(he_calls)"; tengig="$(tengig_addr)"
+    r "$h" 'sudo ip link set bond0.53 down'
+    sleep 200                                  # > 2 ticks of a 1m scheduler
+    r "$h" 'sudo ip link set bond0.53 up'
+    sleep 90
+    after="$(he_calls)"
+    if [ "$(( ${after:-0} - ${before:-0} ))" -ge 1 ]; then
+        warn "HE was updated $(( ${after:-0} - ${before:-0} )) time(s) and then had to move back -- this is the 2026-09-06 shape, now reproduced deliberately. Either widen HYSTERESIS or make vif53-pin-boot-disable hold he-tunnel-follow off for the bounce."
+    else
+        pass "no HE churn across a slow WAN bounce"
+    fi
+    # Whatever happened, the tunnel must end up back on the 10 gig.
+    local i
+    for i in $(seq 1 24); do
+        [ "$(tun_src "$h")" = "$tengig" ] && break
+        sleep 10
+    done
+    [ "$(tun_src "$h")" = "$tengig" ] && pass "tunnel returned to the 10 gig address" \
+        || fail "tunnel stuck on $(tun_src "$h") after the 10 gig came back"
+    save_evidence V7-slow-restore
+}
+
+preflight() {
+    log "preflight"
+    local rc=0
+    [ "$(timeout 60 "$HE" status | grep -c 'API bound  : nohost')" = 1 ] \
+        || { fail "the fake HE endpoint is not answering -- run ./labsim-he-endpoint.sh up"; rc=1; }
+    local h
+    for h in "$R1" "$R2"; do
+        [ "$(tun_state "$h")" = absent ] \
+            && { fail "$h has no tun0 -- run --setup first"; rc=1; }
+        [ "$(r "$h" 'systemctl is-active vrrp-wan-reconcile.timer')" = active ] \
+            || { fail "$h vrrp-wan-reconcile.timer not active"; rc=1; }
+        # The reconciler must be the version that knows about the v6 plane, or
+        # every result below measures the OLD behaviour while printing the new
+        # test names -- the failure mode this repo has already been bitten by.
+        r "$h" 'grep -q v6_take /config/vrrp-wan-reconcile' \
+            || { fail "$h has a vrrp-wan-reconcile with no IPv6 plane -- run migration/vrrp-wan-install"; rc=1; }
+    done
+    # Line the sim's endpoint up with whoever actually holds the tunnel. The real
+    # HE remembers where it was pointed; a rebuilt sim endpoint does not, and
+    # he-tunnel-follow will not re-assert because from its side nothing changed.
+    # Does NOT count as an API call, so the invariant-2 assertions stay honest.
+    local m src
+    m="$(holder)"; src="$(tun_src "$m")"
+    if [ -n "$src" ]; then
+        timeout 60 "$HE" point "$src" >/dev/null 2>&1 \
+            || { fail "could not point the sim HE endpoint at $src"; rc=1; }
+    fi
+    [ "$rc" -eq 0 ] && pass "HE endpoint answering and pointed at $src, both routers have tun0 and a v6-aware reconciler"
+    return $rc
+}
+
+case "${1:---all}" in
+  --list)  echo "V0 baseline | V1 clean failover | V2 10gig-down | V3 cold backup | V4 absent source-address | V5 transition invariant | V6 RA deprecation | V7 slow restore"; exit 0 ;;
+  --setup) setup; exit 0 ;;
+  --all)   preflight || exit 1; V0; V1; V2; V3; V4; V5; V6; V7 ;;
+  *)       preflight || exit 1; "$1" ;;
+esac
+
+echo
+[ "$FAILED" -eq 0 ] && { echo "ALL PASS"; exit 0; }
+echo "$FAILED check(s) FAILED"; exit 1

labsim/labsim-k8s-etcd.sh

@@ -0,0 +1,279 @@
+#!/bin/bash
+# A 3-SERVER embedded-etcd k3s cluster in labsim, configured the way PRODUCTION
+# is -- through /etc/rancher/k3s/config.yaml rendered by labctl's own generator.
+#
+# WHY THIS EXISTS, separate from k8s-up.sh. k8s-up.sh is 1 server + 2 agents and
+# drives k3s with inline INSTALL_K3S_EXEC flags. Production is 3 control-plane
+# servers with embedded etcd, configured by config.yaml from k3s-config.ts. The
+# dual-stack conversion touches etcd quorum on all three at once and rolls a
+# config.yaml change one server at a time -- a failure mode a single-server lab
+# structurally cannot show, driven by a mechanism k8s-up.sh does not use. So this
+# harness models the real shape and the real code path, or the rehearsal is
+# theatre.
+#
+#   ./labsim-k8s-etcd.sh up            build the 3-server cluster
+#   ./labsim-k8s-etcd.sh kubeconfig    fetch ./labsim-etcd.kubeconfig
+#   ./labsim-k8s-etcd.sh status        node + etcd health
+#   ./labsim-k8s-etcd.sh down          destroy the three VMs
+#   ./labsim-k8s-etcd.sh render N      print the config.yaml node N would get
+#
+# The config.yaml is produced by:
+#   bastion .../k3s/bin/render-config.js   (the production generator, exported)
+# so if that generator changes shape, this cluster moves with it.
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+source "$SCRIPT_DIR/lib.sh"
+source "$SCRIPT_DIR/ovs.sh"
+
+K8S_VLAN="${K8S_VLAN:-2}"
+NET="${NET:-172.31.2}"
+FIRST_OCTET="${FIRST_OCTET:-31}"          # .31/.32/.33 -- clear of k8s-up.sh's .11-.13
+SERVERS="${SERVERS:-3}"
+MEM="${MEM:-4096}"; CPUS="${CPUS:-2}"; DISK_GB="${DISK_GB:-12}"
+TOKEN="${TOKEN:-labsim-etcd-token}"
+CILIUM_VERSION="${CILIUM_VERSION:-1.19.1}"
+
+DEB_URL="${DEB_URL:-https://cloud.debian.org/images/cloud/trixie/latest/debian-13-genericcloud-amd64.qcow2}"
+DEB_BASE="${DEB_BASE:-$IMG_DIR/debian-13-genericcloud-amd64.qcow2}"
+
+# The production generator, compiled. Built by `npm --prefix bastion/src/modules run build`.
+RENDER="${RENDER:-$SCRIPT_DIR/../bastion/src/modules/dist/modules/k3s/bin/render-config.js}"
+
+node_name() { echo "labsim-etcd$1"; }
+node_ip()   { echo "${NET}.$((FIRST_OCTET + $1 - 1))"; }
+
+# The audit policy the generated config.yaml references. Without the file the
+# apiserver refuses to start (audit-policy-file points at a missing path), which
+# is a silent-looking crash loop. Kept byte-identical to labctl's audit-policy.ts.
+AUDIT_POLICY='apiVersion: audit.k8s.io/v1
+kind: Policy
+rules:
+  - level: Metadata
+    resources:
+    - group: ""
+      resources: ["secrets", "configmaps"]
+  - level: RequestResponse
+    verbs: ["create", "update", "patch", "delete"]
+    resources:
+    - group: ""
+      resources: ["pods", "services", "deployments"]
+  - level: None
+    resources:
+    - group: ""
+      resources: ["endpoints", "events"]
+    users: ["system:kube-proxy", "system:apiserver"]
+  - level: Metadata
+    omitStages:
+    - "RequestReceived"'
+
+# Render node N's config.yaml with the production generator. Node 1 is
+# cluster-init; 2..N join as SERVERS (not agents) -- role=infra with a server
+# URL is exactly a joining etcd member, the same as production worker1/worker2.
+render_config() {
+  local n="$1"
+  local ip; ip="$(node_ip "$n")"
+  local server1; server1="$(node_ip 1)"
+  if [ "$n" -eq 1 ]; then
+    ROLE=infra HOSTNAME="$(node_name 1)" IP="$ip" TLS_SANS="$ip" \
+      node "$RENDER"
+  else
+    ROLE=infra HOSTNAME="$(node_name "$n")" IP="$ip" TLS_SANS="$ip" \
+      K3S_SERVER_URL="https://${server1}:6443" K3S_TOKEN="$TOKEN" \
+      node "$RENDER"
+  fi
+}
+
+ensure_base_image() {
+  [ -f "$DEB_BASE" ] && { log "base image present"; return; }
+  log "fetching Debian cloud image -> $DEB_BASE"
+  sudo mkdir -p "$IMG_DIR"
+  sudo curl -fsSL --retry 3 -o "${DEB_BASE}.tmp" "$DEB_URL" || die "fetch failed"
+  sudo mv "${DEB_BASE}.tmp" "$DEB_BASE"
+}
+
+build_seed() {
+  local iso="$1" n="$2" pubkey="$3"
+  local vm; vm="$(node_name "$n")"; local ip; ip="$(node_ip "$n")"
+  local server1; server1="$(node_ip 1)"
+  local tmp; tmp="$(mktemp -d)"
+  local cfg; cfg="$(render_config "$n")"
+
+  cat > "$tmp/meta-data" <<EOF
+instance-id: $vm
+local-hostname: $vm
+EOF
+  cat > "$tmp/network-config" <<EOF
+version: 2
+ethernets:
+  enp1s0:
+    match: { name: "en*" }
+    addresses: [$ip/24]
+    routes: [{ to: default, via: ${NET}.1 }]
+    nameservers: { addresses: [8.8.8.8, 1.1.1.1] }
+EOF
+
+  # config.yaml and audit policy embedded via write_files, indented for YAML.
+  local cfg_ind audit_ind
+  cfg_ind="$(printf '%s\n' "$cfg" | sed 's/^/      /')"
+  audit_ind="$(printf '%s\n' "$AUDIT_POLICY" | sed 's/^/      /')"
+
+  cat > "$tmp/user-data" <<EOF
+#cloud-config
+hostname: $vm
+users:
+  - name: debian
+    groups: [sudo]
+    shell: /bin/bash
+    sudo: ["ALL=(ALL) NOPASSWD:ALL"]
+    lock_passwd: false
+    plain_text_passwd: labsim
+    ssh_authorized_keys: [ $pubkey ]
+ssh_pwauth: true
+ssh_authorized_keys: [ $pubkey ]
+
+package_update: true
+packages: [curl, jq, iproute2, tcpdump, etcd-client]
+
+write_files:
+  - path: /etc/rancher/k3s/config.yaml
+    content: |
+$cfg_ind
+  - path: /etc/rancher/k3s/audit-policy.yaml
+    content: |
+$audit_ind
+  - path: /etc/modules-load.d/cilium.conf
+    content: |
+      br_netfilter
+      overlay
+  # The CIS sysctls the generated config's `protect-kernel-defaults: true`
+  # REQUIRES -- byte-for-byte from labctl's sysctl.ts (applyCisHardening), plus
+  # v6 forwarding. Without vm.overcommit_memory=1 / kernel.panic=10 /
+  # kernel.panic_on_oops=1 the kubelet REFUSES to start ("invalid kernel flag"),
+  # k3s exits 1 and crash-loops -- which presents downstream as etcd
+  # re-initialising and the apiserver flapping, i.e. it looks like an etcd/CPU
+  # problem when it is not. In production these come from install.ks.ts + this
+  # operation; the sim must set them too.
+  - path: /etc/sysctl.d/90-k3s-cis.conf
+    content: |
+      net.bridge.bridge-nf-call-iptables  = 1
+      net.bridge.bridge-nf-call-ip6tables = 1
+      net.ipv4.ip_forward                 = 1
+      net.ipv6.conf.all.forwarding        = 1
+      vm.panic_on_oom                     = 0
+      vm.overcommit_memory                = 1
+      kernel.panic                        = 10
+      kernel.panic_on_oops                = 1
+      fs.inotify.max_user_instances       = 524288
+      fs.inotify.max_user_watches         = 524288
+
+runcmd:
+  - [ modprobe, br_netfilter ]
+  - [ modprobe, overlay ]
+  - [ sysctl, --system ]
+  - |
+    # Joining servers must wait for the cluster-init server's API, or the join
+    # races etcd bootstrap and the unit backs off for minutes.
+    if [ "$n" -ne 1 ]; then
+      for i in \$(seq 1 90); do
+        curl -sk --max-time 3 https://${server1}:6443/ping >/dev/null 2>&1 && break
+        sleep 5
+      done
+    fi
+  - |
+    # INSTALL_K3S_EXEC=server (bare) -- everything else comes from config.yaml,
+    # exactly as production. The token is passed via env for the join; on node 1
+    # it seeds the cluster token.
+    #
+    # The etcd-arg tuning is LAB-ONLY (not in production's config): relaxed
+    # heartbeat/election timers so etcd tolerates nested-virt scheduling jitter.
+    # NB: this was NOT what fixed the first run's failure -- that was the missing
+    # protect-kernel-defaults sysctls above, which crash-looped the kubelet and
+    # only LOOKED like etcd instability. The tuning is kept as cheap defensive
+    # insurance for a busy host; it changes nothing the conversion test
+    # exercises.
+    curl -sfL https://get.k3s.io | INSTALL_K3S_EXEC="server --etcd-arg=heartbeat-interval=500 --etcd-arg=election-timeout=5000" K3S_TOKEN="$TOKEN" sh -
+EOF
+
+  # Guard the generated YAML before building the ISO -- a bad indent in the
+  # embedded config.yaml would fail on the node, minutes later and opaquely.
+  python3 -c "import yaml,sys; yaml.safe_load(open(sys.argv[1]))" "$tmp/user-data" \
+    || die "generated user-data is not valid YAML for node $n"
+
+  sudo mkdir -p "$(dirname "$iso")"
+  sudo genisoimage -quiet -output "$iso" -volid cidata -joliet -rock \
+    "$tmp/user-data" "$tmp/meta-data" "$tmp/network-config"
+  rm -rf "$tmp"
+}
+
+create_node() {
+  local n="$1" pubkey="$2"
+  local vm; vm="$(node_name "$n")"; local ip; ip="$(node_ip "$n")"
+  if virsh_q dominfo "$vm" >/dev/null 2>&1; then
+    local st; st="$(virsh_q domstate "$vm" 2>/dev/null | head -1 | tr -d '\n')"
+    [ "$st" = running ] && { log "$vm already running ($ip)"; return; }
+    log "$vm is $st -- starting"; virsh_q start "$vm" >/dev/null; return
+  fi
+  local disk="$IMG_DIR/${vm}.qcow2" seed="$IMG_DIR/${vm}-seed.iso"
+  log "creating $vm ($ip, server ${n}, ${MEM}MB/${CPUS}cpu)"
+  sudo qemu-img create -q -f qcow2 -F qcow2 -b "$DEB_BASE" "$disk" "${DISK_GB}G" >/dev/null
+  build_seed "$seed" "$n" "$pubkey"
+  sudo virt-install --connect "$LIBVIRT_URI" --name "$vm" \
+    --memory "$MEM" --vcpus "$CPUS" \
+    --disk "path=$disk,format=qcow2,bus=virtio" \
+    --disk "path=$seed,device=cdrom" \
+    --network "network=$OVS_NET,portgroup=vlan${K8S_VLAN},model=virtio" \
+    --os-variant debian12 --graphics none --noautoconsole --import >/dev/null
+}
+
+ssh_node() { ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null \
+               -o LogLevel=ERROR -o ConnectTimeout=8 "debian@$1" "$2" 2>/dev/null; }
+
+cmd_up() {
+  require_tools
+  command -v genisoimage >/dev/null || die "genisoimage missing"
+  [ -f "$RENDER" ] || die "render CLI not built: $RENDER (run: npm --prefix bastion/src/modules run build)"
+  local pubkey; pubkey="$(find_ssh_pubkey)"
+  ensure_base_image
+  selected_vlans; log "ensuring OVS fabric"; ovs_up
+  local n; for n in $(seq 1 "$SERVERS"); do create_node "$n" "$pubkey"; done
+  echo
+  log "3 servers booting. Node 1 cluster-inits; 2/3 join as etcd members."
+  log "watch:  ssh debian@$(node_ip 1) 'sudo k3s kubectl get nodes'"
+  log "then:   $0 kubeconfig  &&  $0 status"
+}
+
+cmd_kubeconfig() {
+  local s1; s1="$(node_ip 1)"; local out="$SCRIPT_DIR/labsim-etcd.kubeconfig"
+  ssh_node "$s1" "sudo cat /etc/rancher/k3s/k3s.yaml" | sed "s|127.0.0.1|$s1|" > "$out"
+  chmod 600 "$out"; log "wrote $out"
+}
+
+cmd_status() {
+  local s1; s1="$(node_ip 1)"
+  echo "=== nodes ==="
+  ssh_node "$s1" "sudo k3s kubectl get nodes -o wide 2>/dev/null" | sed 's/^/  /'
+  echo "=== etcd members (quorum needs 2 of 3) ==="
+  ssh_node "$s1" 'sudo k3s kubectl get nodes -l node-role.kubernetes.io/etcd=true --no-headers 2>/dev/null | wc -l' | sed 's/^/  etcd nodes: /'
+  echo "=== servicecidr (both families once dual-stack) ==="
+  ssh_node "$s1" "sudo k3s kubectl get servicecidr -o jsonpath='{range .items[*]}{.metadata.name}={.spec.cidrs}{\"\\n\"}{end}' 2>/dev/null" | sed 's/^/  /'
+}
+
+cmd_down() {
+  local n vm
+  for n in $(seq 1 "$SERVERS"); do
+    vm="$(node_name "$n")"
+    virsh_q destroy "$vm" >/dev/null 2>&1 || true
+    virsh_q undefine "$vm" --remove-all-storage >/dev/null 2>&1 || true
+    log "removed $vm"
+  done
+}
+
+case "${1:-up}" in
+  up)         cmd_up ;;
+  kubeconfig) cmd_kubeconfig ;;
+  status)     cmd_status ;;
+  down)       cmd_down ;;
+  render)     render_config "${2:-1}" ;;
+  *) die "usage: $0 {up|kubeconfig|status|down|render N}" ;;
+esac

labsim/labsim-matrix.py

@@ -78,9 +78,15 @@ def load_vlans() -> list[dict]:
             line = line.strip()
             if not line or line.startswith("#"):
                 continue
-            vid, name, prefix, real = line.split(":", 3)
+            # masklen and host_octet are optional trailing fields; VLAN 10 sets
+            # both because it must be a /23 (see vlans.conf).
+            parts = line.split(":")
+            vid, name, prefix, real = parts[0], parts[1], parts[2], parts[3]
+            masklen = int(parts[4]) if len(parts) > 4 and parts[4] else 24
+            host = parts[5] if len(parts) > 5 and parts[5] else "2"
             vlans.append({"vid": vid, "name": name, "ip": f"{prefix}.10",
-                          "label": f"{vid}:{name}", "real": real})
+                          "label": f"{vid}:{name}", "real": real,
+                          "masklen": masklen, "host_ip": f"{prefix}.{host}"})
     return vlans
 
 

labsim/labsim-pppoe-ha-test.sh

@@ -0,0 +1,381 @@
+#!/bin/bash
+# Does the WAN follow VRRP mastership, and does exactly ONE router ever hold the
+# ISP session?
+#
+# The question is not "did a client get internet". A client can be answered by
+# the wrong path entirely -- for months labsim-vyos's only default route was the
+# libvirt-NAT scaffold on eth2, so every "the LAN still has internet" verdict was
+# answered by eth2 rather than by the WAN under test. This script therefore
+# refuses to run while that is true, and asks its questions of the ROUTERS and
+# the ACCESS CONCENTRATOR, which cannot be answered by accident.
+#
+# The invariant, checked continuously and independently of any individual test:
+#
+#     the AC never reports two `simdsl` sessions, and no two routers ever have a
+#     pppoe0 interface at the same time
+#
+# A run that violates it FAILS regardless of its own verdict, because a single
+# consumer credential is the whole constraint the design exists to satisfy.
+#
+#   ./labsim-pppoe-ha-test.sh --list
+#   ./labsim-pppoe-ha-test.sh T3
+#   ./labsim-pppoe-ha-test.sh --all
+set -uo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+R1="${R1:-172.31.1.252}"; R2="${R2:-172.31.1.253}"
+ISP="${ISP:-192.168.122.63}"          # the fake access concentrator
+LANVM="${LANVM:-172.31.10.10}"
+VIP="${VIP:-172.31.1.1}"
+PW="${VYOS_PW:-vyos}"; LANPW="${LANPW:-labsim}"
+EVID="$SCRIPT_DIR/wan-failover-evidence"
+
+SSH=(-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null
+     -o LogLevel=ERROR -o ConnectTimeout=6 -o PreferredAuthentications=password)
+r()   { timeout 45 sshpass -p "$PW" ssh "${SSH[@]}" "vyos@$1" "${@:2}" 2>/dev/null; }
+isp() { timeout 30 sshpass -p "$PW" ssh "${SSH[@]}" "vyos@$ISP" "$@" 2>/dev/null; }
+
+# Set the AC's session policy, and PROVE it landed.
+#
+# `vbash -c 'source script-template; configure; ...; commit'` does NOT work: the
+# config session never starts and commit dies with "Invalid command: [commit]",
+# on stderr, which the isp() helper discards. The whole T4 matrix therefore ran
+# all three iterations against the accel-ppp DEFAULT while printing
+# "--- session-control=deny ---" -- it reported coverage it did not have, which
+# is worse than reporting a failure. Drive it from a real script FILE, then read
+# the value back and abort the run if it disagrees.
+isp_session_control() {
+    local mode="$1"
+    printf '#!/bin/vbash\nsource /opt/vyatta/etc/functions/script-template\nconfigure\nset service pppoe-server session-control %s\ncommit\nsave\nexit\n' "$mode" \
+        | timeout 30 sshpass -p "$PW" ssh "${SSH[@]}" "vyos@$ISP" 'cat > /tmp/set-sc.sh && chmod +x /tmp/set-sc.sh && sudo /tmp/set-sc.sh' >/dev/null 2>&1
+    local got
+    got="$(isp '/opt/vyatta/bin/vyatta-op-cmd-wrapper show configuration commands' \
+             | sed -n "s/.*session-control '\\(.*\\)'/\\1/p")"
+    if [ "$got" = "$mode" ]; then
+        log "    AC session-control=$mode (verified)"
+        return 0
+    fi
+    fail "could not set AC session-control=$mode (reads '${got:-unset}') -- results would be fiction"
+    return 1
+}
+# The LAN VMs are Alpine and their sshd offers keyboard-interactive, not
+# `password`. Reusing the routers' option set here made ssh exit 255 BEFORE
+# running anything, and T5 read that as "the LAN lost the internet" while a
+# tcpdump on the router showed the pings flowing out pppoe0 and the replies
+# coming back. An exit code that can mean "the network is broken" or "I could
+# not log in" is not a connectivity test.
+LAN_SSH=(-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null
+         -o LogLevel=ERROR -o ConnectTimeout=6)
+lan() { timeout 45 sshpass -p "$LANPW" ssh "${LAN_SSH[@]}" "root@$LANVM" "$@" 2>/dev/null; }
+
+# Assert on what the guest actually reported, not on ssh's exit status.
+lan_online() { [ "$(lan 'ping -c2 -W3 9.9.9.9 >/dev/null 2>&1 && echo ONLINE')" = ONLINE ]; }
+
+log()  { printf '\033[36m==>\033[0m %s\n' "$*"; }
+pass() { printf '  \033[32mPASS\033[0m %s\n' "$*"; }
+fail() { printf '  \033[31mFAIL\033[0m %s\n' "$*"; FAILED=$((FAILED+1)); }
+FAILED=0
+
+# --- observations ----------------------------------------------------------
+ac_sessions() { isp '/opt/vyatta/bin/vyatta-op-cmd-wrapper show pppoe-server sessions' \
+                  | grep -c ' simdsl ' || true; }
+ac_detail()   { isp '/opt/vyatta/bin/vyatta-op-cmd-wrapper show pppoe-server sessions'; }
+# A destroyed or unreachable router is emphatically NOT holding pppoe0, but ssh
+# returns an EMPTY string rather than 0 -- and `[ "" = 0 ]` is false, so a
+# hard-failover test waited for the dead box to "report" zero and hung until its
+# timeout, long after the survivor had taken over correctly. Default to 0.
+ppp_on()      { local v; v="$(r "$1" 'ip -4 addr show pppoe0 2>/dev/null | grep -c inet' | tr -d ' \n')"
+                echo "${v:-0}"; }
+holder()      { for h in "$R1" "$R2"; do
+                  [ "$(r "$h" "ip -4 -o addr show | grep -c ' ${VIP}/'" | tr -d ' \n')" != 0 ] \
+                    && { echo "$h"; return; }; done; echo none; }
+status()      { r "$1" 'sudo /config/vrrp-wan-reconcile --status'; }
+
+# How many routers currently hold a PPPoE interface. The invariant's other half.
+ppp_holders() { n=0; for h in "$R1" "$R2"; do
+                  [ "$(ppp_on "$h")" != 0 ] && n=$((n+1)); done; echo "$n"; }
+
+warn() { printf '  \033[33mWARN\033[0m %s\n' "$*"; }
+
+check_invariant() {
+    local s p ok=0
+    s="$(ac_sessions)"; p="$(ppp_holders)"
+
+    # THE invariant. Two of OUR routers dialled at once is the failure that
+    # matters: one ISP account, and against a real ISP that is how you get
+    # rate-limited or locked out.
+    [ "${p:-0}" -le 1 ] || { fail "INVARIANT: $p routers hold pppoe0"; ok=1; }
+
+    # The AC's session count is a PROXY for the above, and only a valid one
+    # while the AC enforces single-session. Under session-control=disable it
+    # does not, so a destroyed router's session simply stays in the table and
+    # the count reads 2 while exactly one live router is dialled -- which is AC
+    # bookkeeping, not a double dial. Attribute it rather than failing blind:
+    # only call it a violation when more than one router is ACTUALLY dialled.
+    #
+    # Do not silence it either. An orphaned session still occupies the single
+    # slot at a real ISP, and that is exactly what made session-control=deny
+    # take 148s while the survivor's dial attempts were refused.
+    if [ "${s:-0}" -gt 1 ]; then
+        if [ "${p:-0}" -gt 1 ]; then
+            fail "INVARIANT: AC reports $s simdsl sessions AND $p routers are dialled"
+            ok=1
+        else
+            warn "AC reports $s simdsl sessions but only ${p:-0} router is dialled -- stale session from the destroyed peer (expected where the AC does not enforce single-session; it is what a hostile AC holds against the survivor)"
+        fi
+    fi
+    return $ok
+}
+
+# --- preconditions ---------------------------------------------------------
+# The scaffold check is a hard gate, not a warning. A default route via eth2
+# means the box can reach the internet without the WAN working at all, and every
+# connectivity verdict below would be a lie.
+preflight() {
+    log "preflight"
+    local rc=0
+    for h in "$R1" "$R2"; do
+        if r "$h" 'ip route show default' | grep -q 'dev eth2'; then
+            fail "$h still routes via eth2 (libvirt-NAT scaffold) -- run sim-net-config.py --drop-scaffold"
+            rc=1
+        fi
+        if [ "$(r "$h" '[ -f /etc/systemd/system/ppp@pppoe0.service.d/10-vrrp-wan-gate.conf ] && echo y')" != y ]; then
+            fail "$h is missing the ppp gate drop-in -- run migration/vrrp-wan-install"
+            rc=1
+        fi
+        [ "$(r "$h" 'systemctl is-active vrrp-wan-guard.timer')" = active ] \
+            || { fail "$h vrrp-wan-guard.timer not active"; rc=1; }
+        # A router with no peers file CANNOT dial, and says so only once in the
+        # journal. Every failover result in the run would then be a false
+        # negative blamed on the ISP. Check both, and check the config that
+        # renders it -- an unsaved commit reverts on reboot and takes pppoe0
+        # with it, which is how the sim secondary silently stopped dialling.
+        if [ "$(r "$h" '[ -f /etc/ppp/peers/pppoe0 ] && echo y')" != y ]; then
+            fail "$h has no /etc/ppp/peers/pppoe0 -- it cannot dial; re-commit the pppoe subtree"
+            rc=1
+        fi
+        # The op-mode WRAPPER, not a bare `show`: over non-interactive ssh the
+        # bare form is not on PATH, so this silently matched nothing and failed
+        # both routers that were in fact configured correctly.
+        if ! r "$h" '/opt/vyatta/bin/vyatta-op-cmd-wrapper show configuration commands' 2>/dev/null | grep -q 'interfaces pppoe pppoe0 source-interface'; then
+            fail "$h has no pppoe0 in config (unsaved commit lost on reboot?)"
+            rc=1
+        fi
+    done
+    [ "$rc" -eq 0 ] && pass "scaffold dropped, gate present, guard running, both can dial"
+    return $rc
+}
+
+settle() {  # wait until exactly one router holds pppoe0, or give up
+    local i
+    for i in $(seq 1 "${1:-24}"); do
+        [ "$(ppp_holders)" = 1 ] && return 0
+        sleep 5
+    done
+    return 1
+}
+
+# Wait until a SPECIFIC router holds pppoe0 and the other does not.
+#
+# The obvious `settle` is wrong for a failover: "exactly one holder" is already
+# true before the handover starts, so it returns instantly and the test reports
+# that nothing moved while the handover is still in flight. Asking who holds it
+# is the only useful form of the question.
+settle_on() {
+    local want="$1" other i
+    other=$([ "$want" = "$R1" ] && echo "$R2" || echo "$R1")
+    for i in $(seq 1 "${2:-30}"); do
+        [ "$(ppp_on "$want")" != 0 ] && [ "$(ppp_on "$other")" = 0 ] && return 0
+        sleep 5
+    done
+    return 1
+}
+
+save_evidence() {
+    local name="$1"; local d="$EVID/$name"; mkdir -p "$d"
+    { echo "=== $(date -Is) ==="; echo "--- AC sessions ---"; ac_detail
+      for h in "$R1" "$R2"; do echo "--- $h ---"; status "$h"
+        r "$h" 'ip -4 -br addr show pppoe0 2>/dev/null; ip route show default; sudo journalctl -t vrrp-wan -n 8 --no-pager'
+      done; } > "$d/state.txt" 2>&1
+    log "evidence -> wan-failover-evidence/$name/"
+}
+
+# --- tests -----------------------------------------------------------------
+T0() {  # baseline
+    log "T0  baseline: exactly one session, held by the VIP holder"
+    local h s; h="$(holder)"; s="$(ac_sessions)"
+    [ "$s" = 1 ] && pass "AC reports 1 session" || fail "AC reports $s sessions"
+    [ "$(ppp_on "$h")" != 0 ] && pass "the VIP holder ($h) is the one dialled" \
+        || fail "VIP holder $h has no pppoe0"
+    local other; other=$([ "$h" = "$R1" ] && echo "$R2" || echo "$R1")
+    [ "$(ppp_on "$other")" = 0 ] && pass "the backup ($other) is not dialled" \
+        || fail "backup $other also holds pppoe0"
+    save_evidence T0-baseline
+}
+
+T3() {  # clean, deliberate failover
+    log "T3  clean failover via force-fault"
+    local from to t0 t1; from="$(holder)"
+    to=$([ "$from" = "$R1" ] && echo "$R2" || echo "$R1")
+    log "    master=$from -> expecting $to"
+    t0=$(date +%s)
+    r "$from" 'sudo mkdir -p /run/vrrp-wan && sudo touch /run/vrrp-wan/force-fault'
+    if settle_on "$to" 30; then
+        t1=$(date +%s)
+        [ "$(ppp_on "$to")" != 0 ] && pass "pppoe0 moved to $to in $((t1-t0))s" \
+            || fail "pppoe0 did not move to $to"
+        [ "$(ppp_on "$from")" = 0 ] && pass "$from released pppoe0" \
+            || fail "$from still holds pppoe0"
+    else
+        fail "never settled to exactly one pppoe0 holder"
+    fi
+    check_invariant
+    save_evidence T3-clean-failover
+    r "$from" 'sudo rm -f /run/vrrp-wan/force-fault'
+    settle 30 >/dev/null
+}
+
+T5() {  # 10gig down -> PPPoE carries traffic
+    log "T5  10 gig down on the master: traffic must survive on pppoe0"
+    local h; h="$(holder)"
+    r "$h" 'sudo ip link set bond0.53 down'
+    sleep 20
+    local via; via="$(r "$h" 'ip route show default' | head -1)"
+    if echo "$via" | grep -q pppoe0; then
+        pass "default route moved to pppoe0: $via"
+    else
+        fail "default route did not move to pppoe0: ${via:-<none>}"
+    fi
+    # Poll, do not sample. Judging connectivity on one ping 20s after the link
+    # dropped failed while the path was still reconverging, and reported "the LAN
+    # lost the internet" for a path that came back moments later. A single
+    # negative sample is the least trustworthy verdict this harness can produce.
+    local ok=no i
+    for i in $(seq 1 12); do
+        lan_online && { ok=yes; break; }
+        sleep 5
+    done
+    [ "$ok" = yes ] && pass "LAN reaches the internet over pppoe0 (after $((i*5))s)" \
+        || fail "LAN never regained the internet with only pppoe0 up (60s)"
+    save_evidence T5-tengig-down
+    r "$h" 'sudo ip link set bond0.53 up'
+    sleep 20
+}
+
+T11() { # a blessed box with no peers file must not restart-loop
+    log "T11 missing peers file must not restart-loop"
+    local h; h="$(holder)"
+    # COPY then remove, never move: only a commit touching the pppoe subtree
+    # re-renders this file, so losing it strands the box permanently -- the gate
+    # blocks every dial, systemd says "skipped because of an unmet condition
+    # check" exactly once, and nothing else complains. An earlier `mv` pair did
+    # exactly that to the sim secondary and cost a debugging session.
+    r "$h" 'sudo cp -a /etc/ppp/peers/pppoe0 /run/peers.bak && sudo rm -f /etc/ppp/peers/pppoe0; sudo systemctl restart ppp@pppoe0'
+    sleep 12
+    local n; n="$(r "$h" 'systemctl show ppp@pppoe0 -p NRestarts --value')"
+    [ "${n:-99}" -le 1 ] && pass "NRestarts=$n (gate refused the start)" \
+        || fail "NRestarts=$n -- restart loop is back"
+    # Restore on the SAME host we broke, and prove it landed. Do not trust the
+    # copy back: if it silently failed, every later test in the run would be
+    # measuring a router that physically cannot dial.
+    r "$h" 'sudo cp -a /run/peers.bak /etc/ppp/peers/pppoe0'
+    if r "$h" 'test -f /etc/ppp/peers/pppoe0'; then
+        pass "peers file restored on $h"
+    else
+        fail "peers file NOT restored on $h -- that router can no longer dial"
+    fi
+    save_evidence T11-no-peers-file
+    settle 24 >/dev/null
+}
+
+T8() {  # lease expiry: the guard must hang up a demoted-but-unreconciled box
+    log "T8  lease expiry revokes the session"
+    local h; h="$(holder)"
+    r "$h" 'sudo systemctl stop vrrp-wan-reconcile.timer'
+    r "$h" 'sudo touch -d "-200 seconds" /run/vrrp-wan/may-dial'
+    sleep 12
+    [ "$(ppp_on "$h")" = 0 ] && pass "guard hung up on a stale lease" \
+        || fail "stale lease did not revoke the session"
+    r "$h" 'sudo systemctl start vrrp-wan-reconcile.timer'
+    save_evidence T8-lease-expiry
+    settle 24 >/dev/null
+}
+
+
+T4() {  # hard failover across all three AC session-control policies
+    log "T4  hard failover (destroy the master) x session-control"
+    # Vodafone's policy is unknowable from here, so prove the design survives
+    # every one VyOS can express. `replace` is the accel-ppp default and the
+    # friendly case; `deny` is the hostile one, where the AC refuses the second
+    # session until its own dead-peer timer (lcp-echo-interval 30 x failure 3 =
+    # 90s) frees the first -- which is exactly why GRACE is no longer 90.
+    local mode from to vm t0 t1
+    for mode in replace deny disable; do
+        log "    --- session-control=$mode ---"
+        # Skip the iteration rather than measure the wrong policy.
+        isp_session_control "$mode" || continue
+        sleep 5
+        from="$(holder)"; to=$([ "$from" = "$R1" ] && echo "$R2" || echo "$R1")
+        vm=$([ "$from" = "$R1" ] && echo labsim-vyos || echo labsim-vyos2)
+        [ "$from" = none ] && { fail "no master before $mode run"; continue; }
+        log "    destroying $vm (master=$from), expecting $to"
+        t0=$(date +%s)
+        sudo virsh destroy "$vm" >/dev/null 2>&1
+        if settle_on "$to" 48; then
+            t1=$(date +%s)
+            pass "$mode: pppoe0 reached $to in $((t1-t0))s"
+        else
+            fail "$mode: $to never dialled within 240s"
+        fi
+        check_invariant
+        save_evidence "T4-hard-failover-$mode"
+        sudo virsh start "$vm" >/dev/null 2>&1
+        # Re-bond. A VM restart recreates its taps under NEW names, and the OVS
+        # bond keeps the old ones -- lacp dies, VLAN 1 goes with it, and the box
+        # comes back reachable on some VLANs but not others. ovs_bond_router
+        # detects the stale membership and rebuilds, but nothing runs it
+        # automatically, so a destroy/start test must do it or the survivor
+        # looks like a failover failure.
+        ( source "$SCRIPT_DIR/lib.sh"; source "$SCRIPT_DIR/ovs.sh"; selected_vlans
+          LAG_NAME=$([ "$vm" = labsim-vyos ] && echo lag-vyos || echo lag-vyos2)
+          ovs_bond_router "$vm" ) >/dev/null 2>&1
+        # Give the returning box time to boot and settle as BACKUP before the
+        # next iteration; it must NOT dial on the way up.
+        sleep 90
+        [ "$(ppp_on "$from")" = 0 ] && pass "$mode: $from did not dial on reboot" \
+            || fail "$mode: $from dialled on reboot (gate failed)"
+    done
+    isp_session_control replace >/dev/null
+    log "    AC restored to session-control=replace"
+}
+
+T12() { # the flap damper must never tear down an ESTABLISHED session
+    log "T12 flap holdoff must not kill a live session"
+    local h; h="$(holder)"
+    [ "$h" = none ] && { fail "no master to test"; return; }
+    # Forge a holdoff far in the future, as a dial storm would. Before the fix
+    # ppp_dial() returned here BEFORE renewing may-dial, the lease went stale,
+    # and vrrp-wan-guard hung up the master's working WAN ~80s later.
+    r "$h" 'sudo sh -c "echo $(( $(date +%s) + 900 )) > /run/vrrp-wan/holdoff"'
+    # Sleep past LEASE_TTL (75s) so a non-renewed lease would definitely expire.
+    sleep 100
+    if [ "$(ppp_on "$h")" = 1 ]; then
+        pass "session survived a 900s holdoff (lease still renewed)"
+    else
+        fail "holdoff killed the live session -- damper is tearing down the WAN"
+    fi
+    r "$h" 'sudo rm -f /run/vrrp-wan/holdoff /run/vrrp-wan/dials'
+    save_evidence T12-holdoff-keeps-session
+    settle 24 >/dev/null
+}
+
+case "${1:---all}" in
+  --list) echo "T0 baseline | T3 clean failover | T4 hard failover x policy | T5 10gig-down | T8 lease expiry | T11 no-peers-file | T12 holdoff-keeps-session"; exit 0 ;;
+  --all)  preflight || exit 1; T0; T3; T5; T8; T11; T12 ;;
+  --hard) preflight || exit 1; T4 ;;
+  *)      preflight || exit 1; "$1" ;;
+esac
+
+echo
+[ "$FAILED" -eq 0 ] && { echo "ALL PASS"; exit 0; }
+echo "$FAILED check(s) FAILED"; exit 1

labsim/labsim-up.sh

@@ -25,7 +25,8 @@ ovs_up
 
 # --- VMs ------------------------------------------------------------------
 for entry in "${SELECTED[@]}"; do
-  IFS=: read -r vid name prefix real <<<"$entry"
+  parse_vlan_entry "$entry"
+  vid="$V_VID"; name="$V_NAME"; prefix="$V_PREFIX"; real="$V_REAL"
   vm="$(vm_name "$vid" "$name")"
   ip="${prefix}.10"
 
@@ -48,7 +49,7 @@ for entry in "${SELECTED[@]}"; do
   # Copy-on-write overlay: each VM costs a few MB, not 176.
   sudo qemu-img create -q -f qcow2 -F qcow2 -b "$BASE_IMAGE" "$disk" "$VM_DISK" >/dev/null
 
-  build_seed "$seed" "$vm" "$vid" "$name" "$prefix" "$ip" "$real" "$SSH_PUB"
+  build_seed "$seed" "$vm" "$vid" "$name" "$prefix" "$ip" "$real" "$SSH_PUB" "$V_MASK"
 
   sudo virt-install \
     --connect "$LIBVIRT_URI" \

labsim/labsim-vlan-leak-test.sh

@@ -0,0 +1,178 @@
+#!/bin/bash
+# Does the router offer an address from the WRONG VLAN's pool?
+#
+# The fault (ISC Kea #1117, "Mix of physical and virtual interfaces (VLAN) does
+# not work"): with `dhcp-socket-type: raw`, a frame tagged for a sub-interface is
+# ALSO delivered to the PARENT's AF_PACKET socket. Kea then selects a subnet from
+# the parent's own address and answers a second time from the wrong pool. Both
+# offers race to the client and the CLIENT decides which one wins -- which is why
+# the symptom looks device-dependent and unreproducible.
+#
+# Production and this sim have the identical shape that triggers it: Management
+# is the NATIVE/untagged VLAN on `bond0` and therefore has a subnet on the
+# parent, while every other VLAN is a `bond0.<vif>` sub-interface of that same
+# bond.
+#
+# Method: make one DHCP client on a TAGGED VLAN send a DISCOVER, and capture
+# simultaneously on the parent and on the sub-interface. The verdict is not
+# "did the client get the right address" -- the client picking correctly is
+# exactly how this hid for weeks. The verdict is how many OFFERs the SERVER
+# emitted and which source addresses they carried.
+#
+#   ./labsim-vlan-leak-test.sh                 test VLAN 3
+#   ./labsim-vlan-leak-test.sh --vlan 9        test another VLAN
+#   ./labsim-vlan-leak-test.sh --save before   also write the raw captures to
+#                                              vlan-leak-evidence/before/
+set -uo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+
+ROUTER_IP="${ROUTER_IP:-172.31.1.1}"
+ROUTER_PW="${ROUTER_PW:-vyos}"
+CLIENT_PW="${CLIENT_PW:-labsim}"
+VLAN=3
+CLIENT=""
+SAVE=""
+
+while [ $# -gt 0 ]; do
+  case "$1" in
+    --vlan)   VLAN="$2"; shift 2 ;;
+    --client) CLIENT="$2"; shift 2 ;;
+    --save)   SAVE="$2"; shift 2 ;;
+    *) echo "usage: $0 [--vlan N] [--client IP] [--save LABEL]" >&2; exit 2 ;;
+  esac
+done
+: "${CLIENT:=172.31.${VLAN}.10}"
+
+log() { printf '\033[36m==>\033[0m %s\n' "$*"; }
+die() { printf '\033[31merror:\033[0m %s\n' "$*" >&2; exit 1; }
+
+command -v sshpass >/dev/null || die "sshpass required"
+
+# A silent router is the one verdict worth double-checking before reporting.
+#
+# Kea can be `is-active` and answering nothing -- it reopens sockets on a retry
+# loop, and some configurations (`listen-interface`, notably) leave individual
+# VLANs dead while the rest work. Both look identical to a one-shot test: "no
+# reply at all". Two opposite and equally wrong conclusions about
+# `listen-interface` came out of believing a single negative run, in both
+# directions, before a retry made the real pattern obvious.
+#
+# Kea's fallback UDP socket appearing is NOT a readiness signal -- it is bound
+# well before the server actually answers. Checked, and it does not work.
+RETRIED="${RETRIED:-0}"
+
+router() {
+  timeout 40 sshpass -p "$ROUTER_PW" ssh -o StrictHostKeyChecking=no \
+    -o ConnectTimeout=8 "vyos@$ROUTER_IP" "$@" 2>/dev/null
+}
+# VyOS's login shell is vbash, which returns 255 on anything it does not like --
+# in particular a backgrounded job. Feeding the script to `bash -s` on stdin
+# sidesteps vbash entirely and is the only reliable way to leave a daemon behind.
+router_sh() {
+  timeout 40 sshpass -p "$ROUTER_PW" ssh -o StrictHostKeyChecking=no \
+    -o ConnectTimeout=8 "vyos@$ROUTER_IP" 'bash -s' 2>/dev/null
+}
+client() {
+  timeout 60 sshpass -p "$CLIENT_PW" ssh -o StrictHostKeyChecking=no \
+    -o ConnectTimeout=8 "root@$CLIENT" "$@" 2>/dev/null
+}
+
+# Which interfaces to watch. The parent is the whole point: after the fix it
+# should carry no DHCP traffic of its own at all.
+PARENT="bond0"
+VIF="bond0.${VLAN}"
+
+log "router $ROUTER_IP -- capturing on $PARENT and $VIF"
+# Kill EVERY tcpdump first, not just ones matching this run's pattern, and count
+# only afterwards. Counting `pgrep -f 'tcpdump -i bond0'` while a stray tcpdump
+# from an earlier session was still running satisfied the >=2 guard with zero of
+# THIS run's captures alive -- and a capture that records nothing reports
+# "the router sent no reply at all", which reads as a DHCP outage. That sent me
+# chasing a fault in the router that was entirely in the test harness.
+started="$(router_sh <<EOF
+sudo pkill -x tcpdump >/dev/null 2>&1
+sleep 1
+sudo rm -f /tmp/leak-*.txt
+sudo nohup tcpdump -i $PARENT -e -nn -l 'udp port 67 or udp port 68' > /tmp/leak-parent.txt 2>/dev/null &
+sudo nohup tcpdump -i $VIF -e -nn -l 'udp port 67 or udp port 68' > /tmp/leak-vif.txt 2>/dev/null &
+sleep 3
+pgrep -c -x tcpdump
+EOF
+)"
+[ "${started:-0}" -eq 2 ] || die "capture did not start on the router (got ${started:-0}, expected exactly 2)"
+
+# -s /bin/true: ask, observe the answer, apply nothing. The client's existing
+# static address is left alone, so this is safe to run against a live sim VM.
+log "client $CLIENT -- sending DISCOVER on VLAN $VLAN"
+client_out="$(client "udhcpc -n -q -f -i eth0 -s /bin/true -t 3 -T 3 2>&1")"
+[ -n "$client_out" ] || die "no response from client $CLIENT"
+
+sleep 2
+router "sudo pkill -x tcpdump" >/dev/null
+parent="$(router 'sudo cat /tmp/leak-parent.txt')"
+vif="$(router 'sudo cat /tmp/leak-vif.txt')"
+
+echo
+echo "--- client ---"
+echo "$client_out" | sed 's/^/  /'
+echo
+echo "--- $PARENT (parent) ---"
+echo "${parent:-  (nothing)}" | sed 's/^/  /'
+echo
+echo "--- $VIF (sub-interface) ---"
+echo "${vif:-  (nothing)}" | sed 's/^/  /'
+echo
+
+if [ -n "$SAVE" ]; then
+  d="$SCRIPT_DIR/vlan-leak-evidence/$SAVE"
+  mkdir -p "$d"
+  printf '%s\n' "$client_out" > "$d/client.txt"
+  printf '%s\n' "$parent"     > "$d/capture-parent.txt"
+  printf '%s\n' "$vif"        > "$d/capture-vif.txt"
+  router '/opt/vyatta/bin/vyatta-op-cmd-wrapper show configuration commands' \
+    | grep -E 'interfaces bonding|vrrp group' > "$d/router-config.txt"
+  log "evidence saved to vlan-leak-evidence/$SAVE/"
+fi
+
+# --- verdict ---------------------------------------------------------------
+# Every BOOTP Reply seen anywhere, reduced to its source address. A reply whose
+# source is not this VLAN's router leg is an offer from the wrong subnet.
+replies="$(printf '%s\n%s\n' "$parent" "$vif" \
+  | grep -o '[0-9.]*\.67 > [0-9.]*\.68' | awk '{print $1}' | sed 's/\.67$//' \
+  | sort -u)"
+want_prefix="172.31.${VLAN}."
+
+echo "=== verdict ==="
+if [ -z "$replies" ]; then
+  if [ "$RETRIED" -eq 0 ]; then
+    log "no reply -- retrying once in 20s before calling DHCP down"
+    sleep 20; RETRIED=1 exec "$0" --vlan "$VLAN" --client "$CLIENT" ${SAVE:+--save "$SAVE"}
+  fi
+  echo "INCONCLUSIVE: the router sent no reply at all, twice -- DHCP is down on VLAN $VLAN"
+  exit 2
+fi
+
+bad=0
+while read -r src; do
+  [ -z "$src" ] && continue
+  case "$src" in
+    "$want_prefix"*) printf '  ok    offer from %s (this VLAN)\n' "$src" ;;
+    *)               printf '  LEAK  offer from %s (WRONG subnet)\n' "$src"; bad=1 ;;
+  esac
+done <<<"$replies"
+
+# The parent carrying any DHCP of its own is the mechanism, not just a symptom:
+# it means the parent still has a subnet kea can match a tagged frame against.
+if printf '%s' "$parent" | grep -q 'ethertype IPv4' \
+   && printf '%s' "$parent" | grep -v 'vlan ' | grep -q '\.67 > '; then
+  echo "  note  $PARENT emitted an UNTAGGED reply -- the parent still serves a subnet"
+fi
+
+echo
+if [ "$bad" -eq 0 ]; then
+  echo "PASS: only this VLAN's pool answered."
+  exit 0
+fi
+echo "FAIL: the router answered from another VLAN's pool (kea #1117)."
+exit 1

labsim/lib.sh

@@ -58,9 +58,32 @@ selected_vlans() {
   [ ${#SELECTED[@]} -gt 0 ] || die "no VLANs selected (checked $CONF)"
 }
 
+# Split one vlans.conf line, applying defaults for the two optional trailing
+# fields. Sets V_VID V_NAME V_PREFIX V_REAL V_MASK V_HOST.
+parse_vlan_entry() {
+  IFS=: read -r V_VID V_NAME V_PREFIX V_REAL V_MASK V_HOST <<<"$1"
+  V_MASK="${V_MASK:-24}"
+  V_HOST="${V_HOST:-2}"
+}
+
+# Dotted netmask for a prefix length — cloud-init's network-config v1 wants the
+# dotted form, not a /len. /24 -> 255.255.255.0, /23 -> 255.255.254.0.
+netmask_for() {
+  local len="$1" i bits out=()
+  for i in 0 1 2 3; do
+    bits=$(( len - i * 8 ))
+    (( bits > 8 )) && bits=8
+    (( bits < 0 )) && bits=0
+    out+=( $(( 256 - 2 ** (8 - bits) )) )
+  done
+  local IFS=.; echo "${out[*]}"
+}
+
 # cloud-init NoCloud seed: static addressing + SSH key + hello-world HTTP.
 build_seed() {
   local iso="$1" vm="$2" vid="$3" name="$4" prefix="$5" ip="$6" real="$7" pubkey="$8"
+  local masklen="${9:-24}"
+  local netmask; netmask="$(netmask_for "$masklen")"
   local tmp; tmp="$(mktemp -d)"
 
   cat > "$tmp/meta-data" <<EOF
@@ -85,7 +108,7 @@ config:
     subnets:
       - type: static
         address: $ip
-        netmask: 255.255.255.0
+        netmask: $netmask
         # Default route via the router under test. Without this the VMs can
         # reach their own /24 and their gateway, but nothing beyond it — which
         # looks exactly like "the router is broken" in the matrix.
@@ -122,14 +145,14 @@ write_files:
       auto eth0
       iface eth0 inet static
         address $ip
-        netmask 255.255.255.0
+        netmask $netmask
         post-up ip route add default via ${prefix}.1 || true
   - path: /var/www/index.html
     content: |
       <html><body>
       <h1>labsim vlan $vid — $name</h1>
       <p>host: $vm</p>
-      <p>address: $ip/24</p>
+      <p>address: $ip/$masklen</p>
       <p>gateway under test: ${prefix}.1</p>
       <p>mirrors production: $real</p>
       </body></html>

labsim/ovs.sh

@@ -17,6 +17,21 @@ OVS_BR="${OVS_BR:-ovs-labsim}"
 OVS_NET="${OVS_NET:-labsim-ovs}"          # libvirt network wrapping the bridge
 LAG_NAME="${LAG_NAME:-lag-vyos}"
 
+# Native (untagged) VLAN on the trunks to the routers. Empty means NONE: every
+# VLAN, Management included, is tagged.
+#
+# This is not a style choice. A native VLAN is what puts a subnet on the bond
+# PARENT (`bond0`) while every other VLAN lives on a sub-interface of it. With
+# `dhcp-socket-type: raw`, kea then receives each tagged frame TWICE -- once on
+# the sub-interface and once on the parent -- and answers from the parent's pool
+# as well, so a client on VLAN 3 is offered a Management address and picks
+# whichever reply arrives first (ISC Kea #1117).
+#
+# Set LABSIM_NATIVE_VLAN=1 to restore the old shape and reproduce the bug:
+#   LABSIM_NATIVE_VLAN=1 ./router-up.sh && ./labsim-vlan-leak-test.sh   # FAIL
+#                        ./router-up.sh && ./labsim-vlan-leak-test.sh   # PASS
+NATIVE_VLAN="${LABSIM_NATIVE_VLAN:-}"
+
 ovs() { sudo ovs-vsctl "$@"; }
 
 ovs_require() {
@@ -25,6 +40,10 @@ ovs_require() {
     || die "could not start openvswitch"
 }
 
+# A comma-separated VLAN list, numerically sorted, for comparing two lists that
+# came from different places and need not agree on order.
+vlan_sorted() { echo "$1" | tr ',' '\n' | grep -v '^$' | sort -n | paste -sd, -; }
+
 # All VLAN ids from the config, comma separated — used for trunk ports.
 vlan_id_list() {
   local ids=()
@@ -41,12 +60,20 @@ ovs_up() {
   # default route (.1 is), so inter-VLAN tests exercise the router, not the
   # host's routing table.
   for entry in "${SELECTED[@]}"; do
-    IFS=: read -r vid _name prefix _real <<<"$entry"
-    local port="hostv${vid}"
-    ovs --may-exist add-port "$OVS_BR" "$port" tag="$vid" \
+    parse_vlan_entry "$entry"
+    local port="hostv${V_VID}"
+    ovs --may-exist add-port "$OVS_BR" "$port" tag="$V_VID" \
       -- set interface "$port" type=internal
     sudo ip link set "$port" up 2>/dev/null || true
-    sudo ip addr replace "${prefix}.2/24" dev "$port"
+    # Drop any address from a previous mask/octet so a changed vlans.conf does
+    # not leave a stale second address on the port.
+    sudo ip -4 addr flush dev "$port" 2>/dev/null || true
+    # host_octet 0 means "no host leg": the WAN transport VLANs belong to the
+    # fake ISPs, and giving the host an address there would misrepresent the
+    # segment -- the whole point is that VyOS reaches an ISP, not the host.
+    if [ "$V_HOST" != "0" ]; then
+      sudo ip addr replace "${V_PREFIX}.${V_HOST}/${V_MASK}" dev "$port"
+    fi
   done
 
   ovs_define_libvirt_net
@@ -64,18 +91,23 @@ ovs_define_libvirt_net() {
 "
   done
 
-  # Trunk: VLAN 1 native/untagged, everything else tagged — the production
-  # shape. libvirt expresses this declaratively via nativeMode='untagged'
-  # (see libvirt formatnetwork.html), so it does not need fixing up by hand.
-  # It also matters functionally: LACPDUs are untagged, and a trunk with no
-  # native VLAN has nowhere to put them.
+  # Trunk: every VLAN tagged, and by default NO native VLAN (see NATIVE_VLAN at
+  # the top of this file for why -- it is the kea #1117 fix, not tidiness).
+  # libvirt expresses a native VLAN declaratively via nativeMode='untagged'
+  # (see libvirt formatnetwork.html), so it needs no fixing up by hand.
+  #
+  # The worry that a trunk with no native VLAN has nowhere to put LACPDUs is
+  # unfounded, and was tested rather than reasoned about: with vlan_mode=trunk
+  # and no tag, `ovs-appctl bond/show` still reports lacp_status: negotiated
+  # with both members enabled. LACPDUs are slow-protocol frames handled per
+  # member, below the VLAN layer.
   local trunk="  <portgroup name='trunk'>
     <vlan trunk='yes'>
 "
   for entry in "${SELECTED[@]}"; do
     IFS=: read -r vid _n _p _r <<<"$entry"
-    if [ "$vid" = "1" ]; then
-      trunk+="      <tag id='1' nativeMode='untagged'/>
+    if [ -n "$NATIVE_VLAN" ] && [ "$vid" = "$NATIVE_VLAN" ]; then
+      trunk+="      <tag id='${vid}' nativeMode='untagged'/>
 "
     else
       trunk+="      <tag id='${vid}'/>
@@ -108,19 +140,59 @@ ${pg}${trunk}</network>"
 ovs_bond_router() {
   local vm="$1"
   local taps
-  # NB: domiflist indents its rows, so anchor on the FIELD not the line —
-  # /^vnet/ silently matches nothing and the bond never gets built.
-  taps="$(virsh_q domiflist "$vm" 2>/dev/null | awk '$1 ~ /^vnet/ {print $1}')"
+  # Two filters, both load-bearing:
+  #
+  #   $1 ~ /^vnet/ -- domiflist indents its rows, so anchor on the FIELD, not
+  #   the line. /^vnet/ silently matches nothing and the bond never gets built.
+  #
+  #   $3 == OVS_NET -- count only the taps on the sim fabric. The primary also
+  #   carries a libvirt-NAT scaffold NIC (see --drop-scaffold in the README), so
+  #   an unfiltered count is 3, and this function's "expected 2" guard then
+  #   skipped the primary's bond entirely while reporting only a warning.
+  taps="$(virsh_q domiflist "$vm" 2>/dev/null \
+          | awk -v net="$OVS_NET" '$1 ~ /^vnet/ && $3 == net {print $1}')"
   local count; count="$(echo "$taps" | grep -c .)"
-  [ "$count" -eq 2 ] || { warn "router $vm has $count tap(s), expected 2 — skipping bond"; return 1; }
-
-  # Already bonded? (idempotent re-runs)
-  if ovs list-ports "$OVS_BR" 2>/dev/null | grep -qx "$LAG_NAME"; then
-    log "LACP bond $LAG_NAME already present"
-    return 0
-  fi
+  [ "$count" -eq 2 ] \
+    || { warn "router $vm has $count tap(s) on $OVS_NET, expected 2 — skipping bond"; return 1; }
 
   local t1 t2; t1="$(echo "$taps" | sed -n 1p)"; t2="$(echo "$taps" | sed -n 2p)"
+  local want; want="$(vlan_id_list)"
+
+  # Already bonded? Re-runs must still reconcile BOTH the VLAN list and the
+  # membership, and each has drawn blood:
+  #
+  #   VLANs -- adding a VLAN to vlans.conf and finding the bond unchanged is how
+  #   a VLAN silently fails to reach a router: interface present, tag missing,
+  #   frames dropped by the switch.
+  #
+  #   MEMBERS -- restarting the VM recreates its taps with NEW names, leaving the
+  #   bond holding two interfaces that no longer exist. `list-ports` still shows
+  #   the bond, so this early return declared success while the router's real
+  #   taps sat in the bridge as two INDEPENDENT ports, each carrying libvirt's
+  #   own portgroup VLAN config. That is how labsim-vyos2 ran for weeks with no
+  #   LACP at all and a native VLAN nobody had asked for -- and it is invisible
+  #   until you change the trunk and only one router follows.
+  if ovs list-ports "$OVS_BR" 2>/dev/null | grep -qx "$LAG_NAME"; then
+    local members; members="$(ovs-appctl-members)"
+    if [ "$members" != "$(printf '%s\n%s' "$t1" "$t2" | sort | paste -sd, -)" ]; then
+      warn "bond $LAG_NAME holds stale members [$members], VM has [$t1,$t2] — rebuilding"
+      ovs --if-exists del-port "$OVS_BR" "$LAG_NAME"
+    else
+      # Compare as SETS. vlan_id_list yields config order (1,2,3,9,10,200,51,53)
+      # while OVS returns its own sorted order, so a raw string compare reports
+      # drift on every run and rewrites a trunk that was already correct.
+      local have; have="$(ovs get port "$LAG_NAME" trunks 2>/dev/null | tr -d '[] ')"
+      if [ "$(vlan_sorted "$want")" != "$(vlan_sorted "$have")" ]; then
+        log "bond $LAG_NAME trunk drift: [$have] -> [$want]; updating"
+        ovs set port "$LAG_NAME" trunks="$want"
+      else
+        log "LACP bond $LAG_NAME already present, trunk correct"
+      fi
+      ovs_set_native "$LAG_NAME"
+      return 0
+    fi
+  fi
+
   log "bonding $t1 + $t2 into $LAG_NAME (LACP active, balance-tcp)"
   ovs del-port "$OVS_BR" "$t1" 2>/dev/null || true
   ovs del-port "$OVS_BR" "$t2" 2>/dev/null || true
@@ -134,15 +206,36 @@ ovs_bond_router() {
   # LACPDUs. Falling back to active-backup brings the links up so negotiation
   # can start.
   #
-  # native-untagged + tag=1 carries the untagged LACPDUs and the management
-  # VLAN, matching production. libvirt's portgroup VLAN config does NOT apply
-  # here — the bond is a port libvirt never created — so set it inline.
-  local tagged; tagged="$(vlan_id_list | tr ',' '\n' | grep -vx 1 | paste -sd, -)"
+  # The VLAN mode is set inline: libvirt's portgroup config does NOT apply here,
+  # because the bond is a port libvirt never created.
   ovs add-bond "$OVS_BR" "$LAG_NAME" "$t1" "$t2" \
-      lacp=active bond_mode=balance-tcp \
-      vlan_mode=native-untagged tag=1 trunks="$tagged" \
+      lacp=active bond_mode=balance-tcp trunks="$want" \
     -- set port "$LAG_NAME" other_config:lacp-time=fast \
     -- set port "$LAG_NAME" other_config:lacp-fallback-ab=true
+  ovs_set_native "$LAG_NAME"
+}
+
+# The bond's current members, sorted and comma-joined, or empty if the bond does
+# not resolve at all (which is itself the stale case worth rebuilding for).
+ovs-appctl-members() {
+  sudo ovs-appctl bond/show "$LAG_NAME" 2>/dev/null \
+    | awk '/^member /{gsub(/:/,"",$2); print $2}' | sort | paste -sd, -
+}
+
+# Apply NATIVE_VLAN to a trunk port.
+#
+# `tag` MUST be removed, not merely left alone, when there is no native VLAN.
+# Setting vlan_mode=trunk while a stale `tag` remains looks correct in
+# `ovs-vsctl list port` -- it prints vlan_mode: trunk right next to tag: 1 --
+# but the port keeps egressing that VLAN untagged. Half an hour went into
+# "the router is ignoring the trunk change" before the tag was the answer.
+ovs_set_native() {
+  local port="$1"
+  if [ -n "$NATIVE_VLAN" ]; then
+    ovs set port "$port" vlan_mode=native-untagged tag="$NATIVE_VLAN"
+  else
+    ovs set port "$port" vlan_mode=trunk -- clear port "$port" tag
+  fi
 }
 
 ovs_bond_status() {

labsim/sim-ha-config.py

@@ -0,0 +1,144 @@
+#!/usr/bin/env python3
+"""Generate the HA config for the labsim VyOS pair.
+
+Exists to answer one question that cannot be answered on a single router, and
+that would otherwise only be discovered at cutover: with kea HA active-passive,
+does exactly ONE box answer a DHCP request?
+
+Mirrors the production shape so the answer transfers:
+
+    router1  172.31.<v>.252   priority 200   DHCP HA primary
+    router2  172.31.<v>.253   priority 100   DHCP HA secondary
+    VIP      172.31.<v>.1     (what clients use as their gateway)
+
+Note the sim's LoT VLAN is a /23 like production, so the VIP prefix differs
+there -- getting that wrong produces a config that commits and then behaves
+subtly wrongly, which is worse than a failure.
+
+  ./sim-ha-config.py --role primary   > r1.conf
+  ./sim-ha-config.py --role secondary > r2.conf
+"""
+from __future__ import annotations
+
+import argparse
+import importlib.util
+import json
+import os
+import sys
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+MIG = os.path.join(HERE, "..", "migration")
+
+# Reuse the DHCP/DNS generator rather than hand-writing subnets: the whole
+# point is that what is proven here and what production gets share a code path.
+_spec = importlib.util.spec_from_file_location(
+    "unifi_to_vyos", os.path.join(MIG, "unifi-to-vyos.py"))
+unifi_to_vyos = importlib.util.module_from_spec(_spec)
+_spec.loader.exec_module(unifi_to_vyos)
+
+# vlan -> (prefix, cidr). LoT is a /23 in the sim, matching production.
+VLANS = {
+    1:   ("172.31.1",   24),
+    2:   ("172.31.2",   24),
+    3:   ("172.31.3",   24),
+    9:   ("172.31.9",   24),
+    10:  ("172.31.10",  23),
+    200: ("172.31.200", 24),
+}
+# VLAN 2 (k8s) also gets a ULA IPv6, so the routers can peer eBGP with the nodes
+# over IPv6 (the neighbors in sim-net-config.py K8S_NODES_V6 = fd00:2::1x). Only
+# VLAN 2 needs it for the BGP rehearsal; a ULA keeps sim traffic out of the real
+# HE /48. Routers hold ::252 / ::253 (no v6 VRRP VIP -- BGP peers the real per-box
+# address, exactly as production).
+VLANS6 = {2: ("fd00:2", 64)}
+DHCP_HA_NAME = "labsim-dhcp-pair"     # must not equal either host-name
+
+
+def group(vlan: int) -> str:
+    return "native" if vlan == 1 else f"vlan{vlan}"
+
+
+def build(role: str) -> list[str]:
+    primary = role == "primary"
+    self_o, peer_o = (252, 253) if primary else (253, 252)
+    prio = 200 if primary else 100
+    out = [f"# labsim VyOS HA -- {role}", ""]
+
+    for vlan, (pfx, cidr) in VLANS.items():
+        g = group(vlan)
+        # EVERY VLAN is a sub-interface, Management (VLAN 1) included. Putting
+        # Management on the bare `bond0` is what gives the parent a subnet, and
+        # kea then answers tagged frames from it as well as from the correct
+        # sub-interface -- clients on other VLANs get offered a Management
+        # address (ISC Kea #1117). See NATIVE_VLAN in ovs.sh; proven by
+        # labsim-vlan-leak-test.sh.
+        iface = f"bond0 vif {vlan}"
+        out += [
+            f"# VLAN {vlan}",
+            # The node's own address replaces the .1 it used to hold directly;
+            # .1 becomes the floating VIP, exactly as production will be.
+            f"delete interfaces bonding {iface} address",
+            f"set interfaces bonding {iface} address '{pfx}.{self_o}/{cidr}'",
+            *([f"set interfaces bonding {iface} address '{VLANS6[vlan][0]}::{self_o}/{VLANS6[vlan][1]}'"]
+              if vlan in VLANS6 else []),
+            f"set high-availability vrrp group {g} interface bond0.{vlan}",
+            f"set high-availability vrrp group {g} vrid {vlan}",
+            f"set high-availability vrrp group {g} address {pfx}.1/{cidr}",
+            f"set high-availability vrrp group {g} priority {prio}",
+            f"set high-availability vrrp group {g} hello-source-address {pfx}.{self_o}",
+            f"set high-availability vrrp group {g} peer-address {pfx}.{peer_o}",
+            f"set high-availability vrrp group {g} no-preempt",
+            f"set high-availability vrrp sync-group MAIN member {g}",
+            "",
+        ]
+
+    out += [
+        "# --- WAN follows VRRP mastership ---",
+        # These four hooks and the health check existed on both live sim VMs but
+        # in NEITHER generator, so `sim-net-apply.sh check` reported "in sync"
+        # while the mechanism under test was pure undetected drift -- exactly
+        # the failure mode this file was written to end.
+        #
+        # The check goes on the SYNC GROUP, not per group: VyOS rejects a
+        # per-group check while the group is in a sync group ("Only sync group
+        # health check will be used").
+        "set high-availability vrrp sync-group MAIN health-check script '/config/vrrp-wan-health'",
+        "set high-availability vrrp sync-group MAIN health-check interval '5'",
+        "set high-availability vrrp sync-group MAIN health-check failure-count '3'",
+        # take and release both exec vrrp-wan-reconcile: one code path, asked at
+        # different moments. `stop` matters as much as `backup` -- a stopped
+        # keepalived is a demotion too, and without it the box would keep the
+        # WAN while holding no VIPs.
+        "set high-availability vrrp sync-group MAIN transition-script master '/config/vrrp-wan-take'",
+        "set high-availability vrrp sync-group MAIN transition-script backup '/config/vrrp-wan-release'",
+        "set high-availability vrrp sync-group MAIN transition-script fault '/config/vrrp-wan-release'",
+        "set high-availability vrrp sync-group MAIN transition-script stop '/config/vrrp-wan-release'",
+        "",
+        "# --- DHCP high-availability ---",
+        "# The thing under test: active-passive should mean exactly one OFFER.",
+        "set service dhcp-server high-availability mode active-passive",
+        f"set service dhcp-server high-availability status {role}",
+        f"set service dhcp-server high-availability name {DHCP_HA_NAME}",
+        f"set service dhcp-server high-availability source-address 172.31.10.{self_o}",
+        f"set service dhcp-server high-availability remote 172.31.10.{peer_o}",
+        "",
+    ]
+
+    inv = json.load(open(os.path.join(MIG, "export", "inventory.json")))
+    dhcp, stats = unifi_to_vyos.build(inv, "sim")
+    out += [l for l in dhcp if l.strip() and not l.startswith("#")]
+    print(f"{role}: {stats['subnets']} subnets, {stats['mappings']} mappings",
+          file=sys.stderr)
+    return out
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--role", choices=("primary", "secondary"), required=True)
+    args = ap.parse_args()
+    sys.stdout.write("\n".join(build(args.role)) + "\n")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())

labsim/sim-net-apply.sh

@@ -0,0 +1,71 @@
+#!/usr/bin/env bash
+# Apply -- or drift-check -- the labsim routing config on all four VMs.
+#
+#   ./sim-net-apply.sh check    what the VMs run vs what sim-net-config.py says
+#   ./sim-net-apply.sh apply    push the generated config over the serial console
+#
+# `check` is the one you want most of the time. The whole failure mode this
+# guards against is somebody (including me) fixing something on a VM over SSH
+# and never writing it down, so the next rebuild silently loses it.
+#
+# Applied over the serial console rather than SSH because a freshly installed
+# sim router holds the same addresses as its peer -- there is a window where it
+# is not safely reachable over the network at all. See console-apply.py.
+set -uo pipefail
+HERE="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+ACTION="${1:-check}"
+WORK="$(mktemp -d)"; trap 'rm -rf "$WORK"' EXIT
+
+# role : vm : address : regex selecting the subtrees this generator owns
+#
+# primary and secondary now own the SAME subtrees. The secondary's used to omit
+# `interfaces pppoe`, `interfaces bonding`, `nat source` and `protocols
+# failover|static`, so `check` was blind to precisely the WAN config the
+# failover mechanism depends on -- it reported "in sync" for a box that had no
+# WAN at all.
+TARGETS=(
+  "primary:labsim-vyos:172.31.1.252:^set (protocols (bgp|failover|static)|policy (prefix-list|route-map)|nat source rule 1[12]0|interfaces (pppoe|bonding bond0 vif 5[13])|firewall (group interface-group LAN|ipv4|ipv6))"
+  "secondary:labsim-vyos2:172.31.1.253:^set (protocols (bgp|failover|static)|policy (prefix-list|route-map)|nat source rule 1[12]0|interfaces (pppoe|bonding bond0 vif 5[13])|firewall (group interface-group LAN|ipv4|ipv6))"
+  "isp-dhcp:labsim-isp-dhcp:192.168.122.136:^set (interfaces ethernet|nat source|service dhcp-server|firewall ipv4 forward|system host-name)"
+  "isp-pppoe:labsim-isp-pppoe:192.168.122.63:^set (interfaces ethernet|nat source|service pppoe-server|firewall ipv4 forward|system host-name)"
+)
+# Sim-only credential; these VMs hold nothing real and are not reachable from
+# outside the hypervisor.
+SSH_OPTS=(-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null
+          -o LogLevel=ERROR -o PreferredAuthentications=password -o ConnectTimeout=5)
+live() { timeout 30 sshpass -p vyos ssh "${SSH_OPTS[@]}" "vyos@$1" \
+           "/opt/vyatta/bin/vyatta-op-cmd-wrapper show configuration commands" 2>/dev/null; }
+# `vif 53 disable` is RUNTIME state, not config drift. The generators declare it
+# on both routers as the safe resting state (only one box may hold the cloned
+# MAC), and vrrp-wan-reconcile removes it on whichever box currently holds the
+# VIP. Comparing it would therefore report drift on the master for ever, and a
+# check that always cries wolf is a check nobody reads.
+norm() { sed "s/'//g" | grep -v 'hw-id\|offload' \
+           | grep -v 'interfaces bonding bond0 vif 53 disable' | sort -u; }
+
+rc=0
+for t in "${TARGETS[@]}"; do
+  IFS=: read -r role vm addr rx <<<"$t"
+  "$HERE/sim-net-config.py" --role "$role" >"$WORK/$role.conf" 2>/dev/null || {
+    printf '  %-11s GENERATE FAILED\n' "$role"; rc=1; continue; }
+
+  if [ "$ACTION" = apply ]; then
+    printf '  %-11s applying to %s over console...\n' "$role" "$vm"
+    "$HERE/console-apply.py" --vm "$vm" --config "$WORK/$role.conf" || rc=1
+    continue
+  fi
+
+  if ! live "$addr" >"$WORK/$role.live" || [ ! -s "$WORK/$role.live" ]; then
+    printf '  %-11s UNREACHABLE (%s)\n' "$role" "$addr"; rc=1; continue
+  fi
+  grep -E '^set ' "$WORK/$role.conf" | norm >"$WORK/$role.g"
+  grep -E "$rx" "$WORK/$role.live" | norm >"$WORK/$role.l"
+  if d="$(diff "$WORK/$role.g" "$WORK/$role.l")" && [ -z "$d" ]; then
+    printf '  %-11s in sync (%s commands)\n' "$role" "$(wc -l <"$WORK/$role.g")"
+  else
+    printf '  %-11s DRIFT — "<" only in code, ">" only on the VM:\n' "$role"
+    printf '%s\n' "$d" | sed 's/^/      /'
+    rc=1
+  fi
+done
+exit $rc

labsim/sim-net-config.py

@@ -0,0 +1,481 @@
+#!/usr/bin/env python3
+"""Generate the labsim routing + WAN config: BGP, dual WAN, and the two ISP VMs.
+
+`sim-ha-config.py` covers the LAN side of the sim routers (addresses, VRRP,
+conntrack-sync, DHCP). This covers everything that makes the sim a rehearsal for
+production routing rather than just a LAN:
+
+  * eBGP between the sim routers and the k3s nodes, carrying the service range
+  * dual WAN -- DHCP on VLAN 53, PPPoE on VLAN 51 -- with health-checked failover
+  * the two ISP VMs that terminate those WANs and NAT to the real internet
+
+All of it previously existed only as running state on the VMs, applied by hand
+over SSH. Rebuilding a VM lost the rehearsal, and nothing recorded *why* any of
+it was shaped the way it is. That is the entire reason this file exists.
+
+  ./sim-net-config.py --role primary   > r1-net.conf
+  ./console-apply.py --vm labsim-vyos  --config r1-net.conf
+
+or apply all four at once with ./sim-net-apply.sh.
+"""
+from __future__ import annotations
+
+import argparse
+import sys
+
+# ---------------------------------------------------------------------------
+# BGP. Numbers match production so what is proven here ports over unchanged.
+# ---------------------------------------------------------------------------
+ROUTER_AS = 65000
+CLUSTER_AS = 65001
+# The service range Cilium advertises. Chosen against a survey of third-party
+# RFC1918 defaults (docker-desktop, tailscale, k3s, EKS...) so it cannot collide
+# with something we adopt later. Production uses the same /22 -- keep them equal.
+SERVICE_CIDR = "10.61.0.0/22"
+K8S_VLAN = 2
+K8S_NODES = ["172.31.2.11", "172.31.2.12", "172.31.2.13"]
+PEER_GROUP = "K8S"
+PFX_LIST = "K8S-SERVICE-IPS"
+RM_IN, RM_OUT = "K8S-IN", "K8S-OUT"
+
+# IPv6 unicast. Production advertises a public Gateway LoadBalancer /64 out of
+# the HE /48 (2001:470:187e:1e00::/64) and peers over VLAN 2 IPv6. The sim proves
+# the MECHANISM -- ipv6-unicast eBGP, prefix-list6, /128 host routes, ECMP -- with
+# a ULA so nothing here can leak into the real /48. Peering is over VLAN 2 v6
+# (nodes' fd00:2::1x <-> routers' fd00:2::25x, set in sim-ha-config.py /
+# k8s-up.sh), directly connected exactly as v4.
+SERVICE_CIDR_V6 = "fd61:1e00::/64"       # sim analog of prod :1e00::/64 LB pool
+K8S_NODES_V6 = ["fd00:2::11", "fd00:2::12", "fd00:2::13"]
+PEER_GROUP_V6 = "K8S6"
+PFX_LIST_V6 = "K8S-SERVICE-IPS-V6"
+RM_IN_V6, RM_OUT_V6 = "K8S-IN6", "K8S-OUT6"
+# One route per node; ECMP across all three. 4 leaves headroom for a fourth node
+# without a config change.
+MAX_PATHS = 4
+# A safety valve, not a capacity plan: a misconfigured Cilium that starts
+# advertising pod CIDRs should tear the session down, not quietly fill the FIB.
+MAX_PREFIX = 100
+
+# ---------------------------------------------------------------------------
+# Dual WAN. The sim ISPs deliberately use TEST-NET-3 (203.0.113.0/24) and
+# TEST-NET-2 (198.51.100.0/24) from RFC 5737: documentation ranges that are
+# guaranteed never to be real destinations, so a leaked sim route cannot
+# blackhole something that matters.
+# ---------------------------------------------------------------------------
+WAN_DHCP_VLAN = 53          # "10gig-equivalent" -- the primary in production
+WAN_PPPOE_VLAN = 51         # "Vodafone-equivalent" -- the backup
+ISP_DHCP_NET = "203.0.113.0/24"
+ISP_DHCP_GW = "203.0.113.1"
+ISP_DHCP_POOL = ("203.0.113.100", "203.0.113.150")
+ISP_PPPOE_NET = "198.51.100.0/24"
+ISP_PPPOE_GW = "198.51.100.1"
+ISP_PPPOE_POOL = ("198.51.100.100", "198.51.100.150")
+# Sim-only fake credentials. Both ends are in this file on purpose: they
+# authenticate nothing real, and splitting them across a secret store would make
+# the sim unreproducible for no security gain. The PRODUCTION PPPoE password
+# lives in /config/wan-secrets on the router and is never in git.
+PPPOE_USER, PPPOE_PASS = "simdsl", "simpass"
+PPPOE_MTU = 1492            # 1500 - 8 bytes of PPPoE header
+PPPOE_AC = "sim-isp"
+
+# Failover probe targets. NOT 8.8.8.8/8.8.4.4: those are `system name-server`,
+# so a probe failure and a DNS failure would be the same event and the router
+# would flap the WAN every time DNS hiccuped.
+PROBE_TARGETS = ["9.9.9.9", "208.67.222.222"]
+# The bug this shape fixes (WI-8, found here, fixed in production): `ping -I
+# bond0.53` binds the SOURCE address but does not make the kernel use that
+# interface's gateway. On a cold boot where PPPoE won the default route, probes
+# for the 10 gig egressed via PPPoE, succeeded, and the 10 gig was still never
+# selected -- the house ran on the backup line silently. Pinning each target as
+# a /32 via `dhcp-interface` forces the probe onto the line being tested.
+WAN_DHCP_DISTANCE = 210     # NOT `no-default-route`, which blanks new_routers
+PPPOE_DISTANCE = 10         #   in the lease file, leaving failover no gateway
+                            #   to install and silently handing the default
+                            #   route to the backup line.
+
+# One MAC, cloned onto BOTH routers' bond0.53, mirroring production's use of the
+# retired USG's WAN2 MAC to keep its DHCP lease. The sim did not model a shared
+# MAC at all, which is exactly why bond0.53 has to stay on the config plane --
+# only VyOS config can move a MAC between boxes. Locally-administered, sim-only.
+WAN_DHCP_MAC = "02:53:10:61:00:53"
+
+SIM_LAN = "172.31.0.0/16"
+
+# The sim routers' own libvirt-NAT uplink, from before the ISP VMs existed. It
+# is a third default route that does not exist in production and quietly masks
+# WAN failures during a failover test. `--drop-scaffold` removes it.
+SCAFFOLD_IF = "eth2"
+SCAFFOLD_NAT_RULE = 100
+
+
+def bgp(role: str) -> list[str]:
+    """eBGP toward the k3s nodes. Identical on both routers except router-id."""
+    octet = 252 if role == "primary" else 253
+    out = [
+        f"# --- BGP: AS{ROUTER_AS} <-> AS{CLUSTER_AS} (k3s/Cilium) ---",
+        # FRR enforces RFC 8212: an eBGP session with no policy establishes but
+        # exchanges ZERO prefixes, silently. Both directions need a policy or
+        # the session looks perfectly healthy and carries nothing.
+        f"set policy prefix-list {PFX_LIST} rule 10 action permit",
+        f"set policy prefix-list {PFX_LIST} rule 10 prefix {SERVICE_CIDR}",
+        # `le 32` because Cilium advertises individual /32 service addresses out
+        # of the pool, not the aggregate.
+        f"set policy prefix-list {PFX_LIST} rule 10 le 32",
+        f"set policy route-map {RM_IN} rule 10 action permit",
+        f"set policy route-map {RM_IN} rule 10 match ip address prefix-list {PFX_LIST}",
+        # Deny everything outbound. The cluster must never learn a default route
+        # from us -- Cilium would install it and blackhole pod egress.
+        f"set policy route-map {RM_OUT} rule 10 action deny",
+        f"set protocols bgp system-as {ROUTER_AS}",
+        f"set protocols bgp parameters router-id 172.31.{K8S_VLAN}.{octet}",
+        f"set protocols bgp address-family ipv4-unicast maximum-paths ebgp {MAX_PATHS}",
+        f"set protocols bgp peer-group {PEER_GROUP} remote-as {CLUSTER_AS}",
+        f"set protocols bgp peer-group {PEER_GROUP} address-family ipv4-unicast route-map import {RM_IN}",
+        f"set protocols bgp peer-group {PEER_GROUP} address-family ipv4-unicast route-map export {RM_OUT}",
+        f"set protocols bgp peer-group {PEER_GROUP} address-family ipv4-unicast maximum-prefix {MAX_PREFIX}",
+    ]
+    out += [f"set protocols bgp neighbor {n} peer-group {PEER_GROUP}" for n in K8S_NODES]
+    # --- IPv6 unicast: same policy shape, over a separate v6 peer-group ---
+    # `prefix-list6` + `match ipv6 address` are the v6 spellings; `le 128` because
+    # Cilium advertises each Gateway LoadBalancer address as a /128, not the
+    # aggregate. Separate peer-group because the neighbors are v6 addresses; the
+    # export deny is the same safety property (never hand the cluster a default).
+    out += [
+        "",
+        f"set policy prefix-list6 {PFX_LIST_V6} rule 10 action permit",
+        f"set policy prefix-list6 {PFX_LIST_V6} rule 10 prefix {SERVICE_CIDR_V6}",
+        f"set policy prefix-list6 {PFX_LIST_V6} rule 10 le 128",
+        f"set policy route-map {RM_IN_V6} rule 10 action permit",
+        f"set policy route-map {RM_IN_V6} rule 10 match ipv6 address prefix-list {PFX_LIST_V6}",
+        f"set policy route-map {RM_OUT_V6} rule 10 action deny",
+        f"set protocols bgp address-family ipv6-unicast maximum-paths ebgp {MAX_PATHS}",
+        f"set protocols bgp peer-group {PEER_GROUP_V6} remote-as {CLUSTER_AS}",
+        f"set protocols bgp peer-group {PEER_GROUP_V6} address-family ipv6-unicast route-map import {RM_IN_V6}",
+        f"set protocols bgp peer-group {PEER_GROUP_V6} address-family ipv6-unicast route-map export {RM_OUT_V6}",
+        f"set protocols bgp peer-group {PEER_GROUP_V6} address-family ipv6-unicast maximum-prefix {MAX_PREFIX}",
+    ]
+    out += [f"set protocols bgp neighbor {n} peer-group {PEER_GROUP_V6}" for n in K8S_NODES_V6]
+    out.append("")
+    return out
+
+
+def wan(drop_scaffold: bool, role: str = "primary") -> list[str]:
+    """Dual WAN + health-checked failover. IDENTICAL on both routers.
+
+    It used to be primary-only, on the grounds that "two PPPoE clients sharing
+    one credential against a single access concentrator is a different failure
+    mode than anything production has". That was backwards: production has
+    exactly that, and by omitting it the sim could not test the one thing most
+    likely to go wrong. The secondary having no WAN is also why it ended up with
+    zero NAT rules while the primary had ten -- the pair was not comparable.
+
+    Both routers therefore get the same WAN config. What differs is the RESTING
+    STATE, and only for the DHCP line:
+
+      bond0.53  `disable` on BOTH. Its lease is bound to a cloned MAC, and two
+                boxes claiming one MAC is the fault this whole design exists to
+                prevent. vrrp-wan-reconcile removes `disable` on the master.
+      pppoe0    enabled on BOTH, never `disable`d. `disable` unlinks
+                /etc/ppp/peers/pppoe0, which is pppd's own options file, so the
+                promotion path destroyed what it needed. Dialling is gated at
+                the systemd unit instead -- see migration/ppp-vrrp-gate.conf.
+    """
+    out = [
+        "# --- WAN: DHCP (primary) + PPPoE (backup), health-checked ---",
+        f"set interfaces bonding bond0 vif {WAN_PPPOE_VLAN} description "
+        f"'WAN1 Vodafone-equivalent (sim ISP PPPoE)'",
+        f"set interfaces bonding bond0 vif {WAN_DHCP_VLAN} address dhcp",
+        f"set interfaces bonding bond0 vif {WAN_DHCP_VLAN} description "
+        f"'WAN3 10gig-equivalent (sim ISP DHCP)'",
+        f"set interfaces bonding bond0 vif {WAN_DHCP_VLAN} dhcp-options "
+        f"default-route-distance {WAN_DHCP_DISTANCE}",
+        # The cloned MAC. Production clones the old USG's WAN2 MAC so the ISP
+        # keeps handing back the same lease; the sim did not model a shared MAC
+        # at all, which is precisely why bond0.53 must stay on the config plane.
+        # Modelling it lets the sim prove the lease returns to the new master.
+        f"set interfaces bonding bond0 vif {WAN_DHCP_VLAN} mac {WAN_DHCP_MAC}",
+        # Safe at rest on BOTH routers: only the VIP holder enables it.
+        f"set interfaces bonding bond0 vif {WAN_DHCP_VLAN} disable",
+        f"set interfaces pppoe pppoe0 source-interface bond0.{WAN_PPPOE_VLAN}",
+        f"set interfaces pppoe pppoe0 authentication username {PPPOE_USER}",
+        f"set interfaces pppoe pppoe0 authentication password {PPPOE_PASS}",
+        f"set interfaces pppoe pppoe0 default-route-distance {PPPOE_DISTANCE}",
+        f"set interfaces pppoe pppoe0 mtu {PPPOE_MTU}",
+        # The ISP's resolvers would otherwise overwrite ours in resolv.conf every
+        # time the session comes up.
+        "set interfaces pppoe pppoe0 no-peer-dns",
+        "",
+        "# Failover: prefer the DHCP WAN, fall back to PPPoE when probes fail.",
+        f"set protocols failover route 0.0.0.0/0 dhcp-interface bond0.{WAN_DHCP_VLAN} metric 1",
+        f"set protocols failover route 0.0.0.0/0 dhcp-interface bond0.{WAN_DHCP_VLAN} check type icmp",
+        f"set protocols failover route 0.0.0.0/0 dhcp-interface bond0.{WAN_DHCP_VLAN} check timeout 5",
+        # any-available, not all: one unreachable public resolver is a normal
+        # internet event, not a reason to abandon a working 10 gig line.
+        f"set protocols failover route 0.0.0.0/0 dhcp-interface bond0.{WAN_DHCP_VLAN} check policy any-available",
+    ]
+    for t in PROBE_TARGETS:
+        out.append(f"set protocols failover route 0.0.0.0/0 dhcp-interface "
+                   f"bond0.{WAN_DHCP_VLAN} check target {t}")
+    out.append("")
+    out.append("# Pin the probe targets to the line under test (WI-8 -- see above).")
+    for t in PROBE_TARGETS:
+        out.append(f"set protocols static route {t}/32 dhcp-interface bond0.{WAN_DHCP_VLAN}")
+    out += [
+        "",
+        "# Masquerade out of whichever WAN currently holds the default route.",
+        f"set nat source rule 110 outbound-interface name bond0.{WAN_DHCP_VLAN}",
+        f"set nat source rule 110 source address {SIM_LAN}",
+        "set nat source rule 110 translation address masquerade",
+        "set nat source rule 120 outbound-interface name pppoe0",
+        f"set nat source rule 120 source address {SIM_LAN}",
+        "set nat source rule 120 translation address masquerade",
+        "",
+    ]
+    if drop_scaffold:
+        out += [
+            "# Remove the pre-ISP-VM libvirt-NAT uplink: a third default route",
+            "# that has no production equivalent and hides real WAN failures.",
+            f"delete interfaces ethernet {SCAFFOLD_IF} address",
+            f"delete nat source rule {SCAFFOLD_NAT_RULE}",
+            "",
+        ]
+    return out
+
+
+# ---------------------------------------------------------------------------
+# Firewall. The policy is: internal VLANs talk to each other and to the
+# internet; the internet initiates nothing inward.
+#
+# That was already the *effect* of the previous IPv4 ruleset, but it was built
+# as a blacklist -- `default-action accept` plus explicit drops on each WAN
+# interface. The result is identical right up until someone adds a WAN, at
+# which point it is wide open and nothing looks wrong. This is the same policy
+# expressed as a whitelist, so a new interface is closed until it is named.
+# ---------------------------------------------------------------------------
+# Management is `bond0.1`, NOT the bare `bond0`. Every VLAN is tagged and the
+# bond parent carries no subnet at all -- see NATIVE_VLAN in ovs.sh for why.
+#
+# This line is the trap in that change. The address move is the visible part and
+# the part you remember; leaving `bond0` here instead of `bond0.1` means the
+# whole Management VLAN falls outside the LAN group, and with a default-deny
+# ruleset that is every management session and all inter-VLAN routing for VLAN 1
+# dropped the instant the commit lands -- on a router you reach through itself.
+LAN_IFACES = ["bond0.1", "bond0.2", "bond0.3", "bond0.9", "bond0.10", "bond0.200"]
+LAN_GROUP = "LAN"
+
+
+def firewall(wan_dhcp_if: str | None = f"bond0.{WAN_DHCP_VLAN}") -> list[str]:
+    """wan_dhcp_if=None on a router with no DHCP WAN -- a firewall rule naming
+    an interface that does not exist is rejected at commit."""
+    out = [f"# --- firewall: LAN-to-anywhere, internet-to-nothing ---"]
+    # Delete each filter before rebuilding it. `set` on a rule number is
+    # ADDITIVE: if a rule 10 already exists carrying an inbound-interface
+    # constraint, `set ... rule 10 state established` silently ANDs onto it,
+    # and you get a stateful-accept rule that only applies to one interface
+    # pair. Observed in labsim: return traffic from the internet matched
+    # neither that rule nor the LAN rule and hit the default drop, so LAN
+    # hosts could reach nothing outbound. Everything here is one commit, so
+    # nftables is rebuilt atomically -- there is no window with no firewall.
+    out += [f"delete firewall {fam} {hook} filter"
+            for fam in ("ipv4", "ipv6") for hook in ("forward", "input")]
+    out += [f"set firewall group interface-group {LAN_GROUP} interface {i}"
+            for i in LAN_IFACES]
+    out += [
+        "",
+        # INPUT -- traffic terminating ON the router.
+        # Loopback first. Under a default-drop input policy, services talking to
+        # 127.0.0.1 are filtered like anything else, and the failures are
+        # bizarre and hard to attribute. Nothing off-box can forge iif lo.
+        "set firewall ipv4 input filter rule 5 action accept",
+        "set firewall ipv4 input filter rule 5 description 'loopback'",
+        "set firewall ipv4 input filter rule 5 inbound-interface name lo",
+        "set firewall ipv4 input filter rule 10 action accept",
+        "set firewall ipv4 input filter rule 10 description 'established/related'",
+        "set firewall ipv4 input filter rule 10 state established",
+        "set firewall ipv4 input filter rule 10 state related",
+        # One rule covers VRRP, conntrack-sync, kea HA, SSH, DNS and BGP,
+        # because every one of them arrives on a LAN interface. Enumerating the
+        # protocols instead would mean a new firewall rule every time the pair
+        # gains a feature -- and a lockout the day someone forgets.
+        f"set firewall ipv4 input filter rule 20 action accept",
+        f"set firewall ipv4 input filter rule 20 description 'trusted LAN to the router'",
+        f"set firewall ipv4 input filter rule 20 inbound-interface group {LAN_GROUP}",
+        # DHCP client. Lease RENEWAL is unicast UDP to port 68 and conntrack
+        # does not reliably cover it, so without this the WAN keeps working
+        # until the lease expires and then dies -- a delayed failure that looks
+        # nothing like a firewall change.
+        "set firewall ipv4 input filter default-action drop",
+        "",
+        # FORWARD -- traffic passing THROUGH the router.
+        "set firewall ipv4 forward filter rule 10 action accept",
+        "set firewall ipv4 forward filter rule 10 description 'established/related'",
+        "set firewall ipv4 forward filter rule 10 state established",
+        "set firewall ipv4 forward filter rule 10 state related",
+        # Inter-VLAN *and* LAN-to-internet in one rule: both are "came in on a
+        # LAN interface". Deliberately no restriction between internal VLANs --
+        # segmenting them is a separate decision, not a side effect of this one.
+        f"set firewall ipv4 forward filter rule 20 action accept",
+        f"set firewall ipv4 forward filter rule 20 description 'LAN to anywhere (inter-VLAN + internet)'",
+        f"set firewall ipv4 forward filter rule 20 inbound-interface group {LAN_GROUP}",
+        "set firewall ipv4 forward filter default-action drop",
+        "",
+        # IPv6 already runs default-deny. It only lacks the loopback rule.
+        "set firewall ipv6 input filter rule 5 action accept",
+        "set firewall ipv6 input filter rule 5 description 'loopback'",
+        "set firewall ipv6 input filter rule 5 inbound-interface name lo",
+        "set firewall ipv6 input filter rule 10 action accept",
+        "set firewall ipv6 input filter rule 10 description 'replies to our own traffic'",
+        "set firewall ipv6 input filter rule 10 state established",
+        "set firewall ipv6 input filter rule 10 state related",
+        # RFC 4890: filtering ICMPv6 wholesale breaks ND and PMTUD, which
+        # presents as "IPv6 works until something large", not as a block.
+        "set firewall ipv6 input filter rule 20 action accept",
+        "set firewall ipv6 input filter rule 20 description 'ICMPv6 - ND/RA/PMTUD'",
+        "set firewall ipv6 input filter rule 20 protocol icmpv6",
+        f"set firewall ipv6 input filter rule 30 action accept",
+        f"set firewall ipv6 input filter rule 30 description 'trusted LAN to the router'",
+        f"set firewall ipv6 input filter rule 30 inbound-interface group {LAN_GROUP}",
+        "set firewall ipv6 input filter default-action drop",
+        "set firewall ipv6 forward filter rule 10 action accept",
+        "set firewall ipv6 forward filter rule 10 description 'replies to our own traffic'",
+        "set firewall ipv6 forward filter rule 10 state established",
+        "set firewall ipv6 forward filter rule 10 state related",
+        "set firewall ipv6 forward filter rule 20 action accept",
+        "set firewall ipv6 forward filter rule 20 description 'ICMPv6 - ND/RA/PMTUD'",
+        "set firewall ipv6 forward filter rule 20 protocol icmpv6",
+        f"set firewall ipv6 forward filter rule 30 action accept",
+        f"set firewall ipv6 forward filter rule 30 description 'trusted LAN interfaces only'",
+        f"set firewall ipv6 forward filter rule 30 inbound-interface group {LAN_GROUP}",
+        "set firewall ipv6 forward filter default-action drop",
+        "",
+    ]
+    if wan_dhcp_if:
+        dhcp = [
+            "set firewall ipv4 input filter rule 140 action accept",
+            "set firewall ipv4 input filter rule 140 description 'DHCP client lease renewal'",
+            "set firewall ipv4 input filter rule 140 protocol udp",
+            "set firewall ipv4 input filter rule 140 destination port 68",
+            f"set firewall ipv4 input filter rule 140 inbound-interface name {wan_dhcp_if}",
+        ]
+        i = out.index("set firewall ipv4 input filter default-action drop")
+        out[i:i] = dhcp
+    return out
+
+
+def isp_dhcp(wan_if: str, uplink_if: str) -> list[str]:
+    """The 10gig-equivalent ISP: hands out a lease, NATs to the real internet."""
+    return [
+        f"# --- sim ISP: DHCP WAN on VLAN {WAN_DHCP_VLAN} ---",
+        "set system host-name isp-dhcp",
+        f"set interfaces ethernet {wan_if} address {ISP_DHCP_GW}/24",
+        f"set interfaces ethernet {wan_if} description "
+        f"'sim ISP - 10gig-equivalent WAN on VLAN{WAN_DHCP_VLAN}'",
+        f"set interfaces ethernet {uplink_if} address dhcp",
+        f"set interfaces ethernet {uplink_if} description 'uplink to the real internet'",
+        f"set service dhcp-server shared-network-name WAN{WAN_DHCP_VLAN} "
+        f"subnet {ISP_DHCP_NET} subnet-id 1",
+        f"set service dhcp-server shared-network-name WAN{WAN_DHCP_VLAN} "
+        f"subnet {ISP_DHCP_NET} option default-router {ISP_DHCP_GW}",
+        f"set service dhcp-server shared-network-name WAN{WAN_DHCP_VLAN} "
+        f"subnet {ISP_DHCP_NET} option name-server 8.8.8.8",
+        f"set service dhcp-server shared-network-name WAN{WAN_DHCP_VLAN} "
+        f"subnet {ISP_DHCP_NET} range CUST start {ISP_DHCP_POOL[0]}",
+        f"set service dhcp-server shared-network-name WAN{WAN_DHCP_VLAN} "
+        f"subnet {ISP_DHCP_NET} range CUST stop {ISP_DHCP_POOL[1]}",
+        "",
+    ] + _isp_common(uplink_if, ISP_DHCP_NET, "sim ISP: NAT customers to the real internet")
+
+
+def isp_pppoe(wan_if: str, uplink_if: str) -> list[str]:
+    """The Vodafone-equivalent ISP: terminates PPPoE, NATs to the real internet."""
+    return [
+        f"# --- sim ISP: PPPoE WAN on VLAN {WAN_PPPOE_VLAN} ---",
+        "set system host-name isp-pppoe",
+        f"set interfaces ethernet {wan_if} description "
+        f"'sim ISP - Vodafone-equivalent WAN on VLAN{WAN_PPPOE_VLAN} (PPPoE)'",
+        f"set interfaces ethernet {uplink_if} address dhcp",
+        f"set interfaces ethernet {uplink_if} description 'uplink to the real internet'",
+        f"set service pppoe-server access-concentrator {PPPOE_AC}",
+        f"set service pppoe-server interface {wan_if}",
+        f"set service pppoe-server gateway-address {ISP_PPPOE_GW}",
+        "set service pppoe-server authentication mode local",
+        f"set service pppoe-server authentication local-users username {PPPOE_USER} "
+        f"password {PPPOE_PASS}",
+        f"set service pppoe-server client-ip-pool CUST range "
+        f"{ISP_PPPOE_POOL[0]}-{ISP_PPPOE_POOL[1]}",
+        "set service pppoe-server default-pool CUST",
+        "set service pppoe-server name-server 8.8.8.8",
+        "",
+    ] + _isp_common(uplink_if, ISP_PPPOE_NET, "sim ISP: NAT PPPoE customers to the real internet")
+
+
+def _isp_common(uplink_if: str, customer_net: str, desc: str) -> list[str]:
+    return [
+        "set nat source rule 100 description " + f"'{desc}'",
+        f"set nat source rule 100 outbound-interface name {uplink_if}",
+        f"set nat source rule 100 source address {customer_net}",
+        "set nat source rule 100 translation address masquerade",
+        "",
+        # An ISP that drops return traffic is not simulating an ISP. The forward
+        # chain defaults to accept here on purpose -- these VMs model the
+        # internet, and the thing under test is the router's firewall, not this.
+        "set firewall ipv4 forward filter default-action accept",
+        "set firewall ipv4 forward filter rule 10 action accept",
+        "set firewall ipv4 forward filter rule 10 state established",
+        "set firewall ipv4 forward filter rule 10 state related",
+        "set firewall ipv4 forward filter rule 10 description conntrack-engage",
+        "",
+    ]
+
+
+def build(role: str, drop_scaffold: bool, wan_if: str, uplink_if: str) -> list[str]:
+    if role in ("primary", "secondary"):
+        # BOTH routers get the identical WAN. The sim used to give it to the
+        # primary only, reasoning that two PPPoE clients sharing one credential
+        # was "a different failure mode than anything production has" -- but
+        # that IS production, and omitting it meant the failover path was the
+        # one path the sim could not exercise. It also left the pair
+        # incomparable: ten NAT rules on one box, none on the other.
+        #
+        # Safety comes from resting state, not from asymmetry: bond0.53 is
+        # `disable`d on both (cloned MAC), pppoe0 is enabled on both but gated
+        # at the systemd unit. See wan() and migration/ppp-vrrp-gate.conf.
+        return ([f"# labsim routing -- {role}", ""]
+                + bgp(role) + wan(drop_scaffold, role)
+                + firewall(wan_dhcp_if=f"bond0.{WAN_DHCP_VLAN}"))
+    if role == "isp-dhcp":
+        return isp_dhcp(wan_if, uplink_if)
+    return isp_pppoe(wan_if, uplink_if)
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--role", required=True,
+                    choices=("primary", "secondary", "isp-dhcp", "isp-pppoe"))
+    ap.add_argument("--drop-scaffold", action="store_true",
+                    help="also remove the pre-ISP-VM libvirt-NAT uplink (primary only)")
+    # The ISP VMs' interface names depend on PCI enumeration order, which is not
+    # stable across a rebuild: isp-dhcp came up as eth0/eth1 and isp-pppoe as
+    # eth2/eth3 from identical XML. Check with `show interfaces` before applying
+    # rather than trusting these defaults.
+    ap.add_argument("--wan-if", default=None, help="ISP VM: customer-facing NIC")
+    ap.add_argument("--uplink-if", default=None, help="ISP VM: internet-facing NIC")
+    args = ap.parse_args()
+
+    defaults = {"isp-dhcp": ("eth0", "eth1"), "isp-pppoe": ("eth2", "eth3")}
+    w, u = defaults.get(args.role, ("", ""))
+    w, u = args.wan_if or w, args.uplink_if or u
+
+    if args.drop_scaffold and args.role != "primary":
+        print("--drop-scaffold only applies to --role primary", file=sys.stderr)
+        return 2
+
+    lines = build(args.role, args.drop_scaffold, w, u)
+    sys.stdout.write("\n".join(lines) + "\n")
+    n = len([l for l in lines if l.startswith(("set ", "delete "))])
+    print(f"{args.role}: {n} commands", file=sys.stderr)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())

labsim/vlan-leak-evidence/after-vlan1/capture-parent.txt

@@ -0,0 +1,6 @@
+12:52:35.919490 52:54:00:6d:71:e7 > ff:ff:ff:ff:ff:ff, ethertype 802.1Q (0x8100), length 346: vlan 1, p 0, ethertype IPv4 (0x0800), 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 52:54:00:6d:71:e7, length 300
+12:52:35.920089 52:54:00:e5:95:a2 > 52:54:00:6d:71:e7, ethertype 802.1Q (0x8100), length 329: vlan 1, p 0, ethertype IPv4 (0x0800), 172.31.1.252.67 > 172.31.1.6.68: BOOTP/DHCP, Reply, length 283
+12:52:35.920307 52:54:00:e5:95:a2 > 52:54:00:6d:71:e7, ethertype 802.1Q (0x8100), length 329: vlan 1, p 0, ethertype IPv4 (0x0800), 172.31.1.252.67 > 172.31.1.7.68: BOOTP/DHCP, Reply, length 283
+12:52:35.922052 52:54:00:6d:71:e7 > ff:ff:ff:ff:ff:ff, ethertype 802.1Q (0x8100), length 346: vlan 1, p 0, ethertype IPv4 (0x0800), 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 52:54:00:6d:71:e7, length 300
+12:52:35.922509 52:54:00:e5:95:a2 > 52:54:00:6d:71:e7, ethertype 802.1Q (0x8100), length 329: vlan 1, p 0, ethertype IPv4 (0x0800), 172.31.1.252.67 > 172.31.1.6.68: BOOTP/DHCP, Reply, length 283
+12:52:35.923327 52:54:00:e5:95:a2 > 52:54:00:6d:71:e7, ethertype 802.1Q (0x8100), length 329: vlan 1, p 0, ethertype IPv4 (0x0800), 172.31.1.252.67 > 172.31.1.6.68: BOOTP/DHCP, Reply, length 283

labsim/vlan-leak-evidence/after-vlan1/capture-vif.txt

@@ -0,0 +1,6 @@
+12:52:35.919490 52:54:00:6d:71:e7 > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 342: 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 52:54:00:6d:71:e7, length 300
+12:52:35.920081 52:54:00:e5:95:a2 > 52:54:00:6d:71:e7, ethertype IPv4 (0x0800), length 325: 172.31.1.252.67 > 172.31.1.6.68: BOOTP/DHCP, Reply, length 283
+12:52:35.920305 52:54:00:e5:95:a2 > 52:54:00:6d:71:e7, ethertype IPv4 (0x0800), length 325: 172.31.1.252.67 > 172.31.1.7.68: BOOTP/DHCP, Reply, length 283
+12:52:35.922052 52:54:00:6d:71:e7 > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 342: 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 52:54:00:6d:71:e7, length 300
+12:52:35.922507 52:54:00:e5:95:a2 > 52:54:00:6d:71:e7, ethertype IPv4 (0x0800), length 325: 172.31.1.252.67 > 172.31.1.6.68: BOOTP/DHCP, Reply, length 283
+12:52:35.923326 52:54:00:e5:95:a2 > 52:54:00:6d:71:e7, ethertype IPv4 (0x0800), length 325: 172.31.1.252.67 > 172.31.1.6.68: BOOTP/DHCP, Reply, length 283

labsim/vlan-leak-evidence/after-vlan1/client.txt

@@ -0,0 +1,4 @@
+udhcpc: started, v1.37.0
+udhcpc: broadcasting discover
+udhcpc: broadcasting select for 172.31.1.6, server 172.31.1.252
+udhcpc: lease of 172.31.1.6 obtained from 172.31.1.252, lease time 86400

labsim/vlan-leak-evidence/after-vlan1/router-config.txt

@@ -0,0 +1,64 @@
+set high-availability vrrp group native address 172.31.1.1/24
+set high-availability vrrp group native hello-source-address '172.31.1.252'
+set high-availability vrrp group native interface 'bond0.1'
+set high-availability vrrp group native no-preempt
+set high-availability vrrp group native peer-address '172.31.1.253'
+set high-availability vrrp group native priority '200'
+set high-availability vrrp group native vrid '1'
+set high-availability vrrp group vlan2 address 172.31.2.1/24
+set high-availability vrrp group vlan2 hello-source-address '172.31.2.252'
+set high-availability vrrp group vlan2 interface 'bond0.2'
+set high-availability vrrp group vlan2 no-preempt
+set high-availability vrrp group vlan2 peer-address '172.31.2.253'
+set high-availability vrrp group vlan2 priority '200'
+set high-availability vrrp group vlan2 vrid '2'
+set high-availability vrrp group vlan3 address 172.31.3.1/24
+set high-availability vrrp group vlan3 hello-source-address '172.31.3.252'
+set high-availability vrrp group vlan3 interface 'bond0.3'
+set high-availability vrrp group vlan3 no-preempt
+set high-availability vrrp group vlan3 peer-address '172.31.3.253'
+set high-availability vrrp group vlan3 priority '200'
+set high-availability vrrp group vlan3 vrid '3'
+set high-availability vrrp group vlan9 address 172.31.9.1/24
+set high-availability vrrp group vlan9 hello-source-address '172.31.9.252'
+set high-availability vrrp group vlan9 interface 'bond0.9'
+set high-availability vrrp group vlan9 no-preempt
+set high-availability vrrp group vlan9 peer-address '172.31.9.253'
+set high-availability vrrp group vlan9 priority '200'
+set high-availability vrrp group vlan9 vrid '9'
+set high-availability vrrp group vlan10 address 172.31.10.1/23
+set high-availability vrrp group vlan10 hello-source-address '172.31.10.252'
+set high-availability vrrp group vlan10 interface 'bond0.10'
+set high-availability vrrp group vlan10 no-preempt
+set high-availability vrrp group vlan10 peer-address '172.31.10.253'
+set high-availability vrrp group vlan10 priority '200'
+set high-availability vrrp group vlan10 vrid '10'
+set high-availability vrrp group vlan200 address 172.31.200.1/24
+set high-availability vrrp group vlan200 hello-source-address '172.31.200.252'
+set high-availability vrrp group vlan200 interface 'bond0.200'
+set high-availability vrrp group vlan200 no-preempt
+set high-availability vrrp group vlan200 peer-address '172.31.200.253'
+set high-availability vrrp group vlan200 priority '200'
+set high-availability vrrp group vlan200 vrid '200'
+set interfaces bonding bond0 description 'api-batch-test'
+set interfaces bonding bond0 hash-policy 'layer2+3'
+set interfaces bonding bond0 lacp-rate 'fast'
+set interfaces bonding bond0 member interface 'eth0'
+set interfaces bonding bond0 member interface 'eth1'
+set interfaces bonding bond0 mode '802.3ad'
+set interfaces bonding bond0 vif 1 address '172.31.1.252/24'
+set interfaces bonding bond0 vif 1 description 'management'
+set interfaces bonding bond0 vif 2 address '172.31.2.252/24'
+set interfaces bonding bond0 vif 2 description 'k8s'
+set interfaces bonding bond0 vif 3 address '172.31.3.252/24'
+set interfaces bonding bond0 vif 3 description 'kvm'
+set interfaces bonding bond0 vif 9 address '172.31.9.252/24'
+set interfaces bonding bond0 vif 9 description 'private'
+set interfaces bonding bond0 vif 10 address '172.31.10.252/23'
+set interfaces bonding bond0 vif 10 description 'lot'
+set interfaces bonding bond0 vif 51 description 'WAN1 Vodafone-equivalent (sim ISP PPPoE)'
+set interfaces bonding bond0 vif 53 address 'dhcp'
+set interfaces bonding bond0 vif 53 description 'WAN3 10gig-equivalent (sim ISP DHCP)'
+set interfaces bonding bond0 vif 53 dhcp-options default-route-distance '210'
+set interfaces bonding bond0 vif 200 address '172.31.200.252/24'
+set interfaces bonding bond0 vif 200 description 'roomates'

labsim/vlan-leak-evidence/after/capture-parent.txt

@@ -0,0 +1,6 @@
+12:52:14.639170 52:54:00:02:2e:b1 > ff:ff:ff:ff:ff:ff, ethertype 802.1Q (0x8100), length 346: vlan 3, p 0, ethertype IPv4 (0x0800), 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 52:54:00:02:2e:b1, length 300
+12:52:14.640467 52:54:00:e5:95:a2 > 52:54:00:02:2e:b1, ethertype 802.1Q (0x8100), length 329: vlan 3, p 0, ethertype IPv4 (0x0800), 172.31.3.252.67 > 172.31.3.11.68: BOOTP/DHCP, Reply, length 283
+12:52:14.640846 52:54:00:e5:95:a2 > 52:54:00:02:2e:b1, ethertype 802.1Q (0x8100), length 329: vlan 3, p 0, ethertype IPv4 (0x0800), 172.31.3.252.67 > 172.31.3.11.68: BOOTP/DHCP, Reply, length 283
+12:52:14.642554 52:54:00:02:2e:b1 > ff:ff:ff:ff:ff:ff, ethertype 802.1Q (0x8100), length 346: vlan 3, p 0, ethertype IPv4 (0x0800), 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 52:54:00:02:2e:b1, length 300
+12:52:14.642766 52:54:00:e5:95:a2 > 52:54:00:02:2e:b1, ethertype 802.1Q (0x8100), length 329: vlan 3, p 0, ethertype IPv4 (0x0800), 172.31.3.252.67 > 172.31.3.11.68: BOOTP/DHCP, Reply, length 283
+12:52:14.643056 52:54:00:e5:95:a2 > 52:54:00:02:2e:b1, ethertype 802.1Q (0x8100), length 329: vlan 3, p 0, ethertype IPv4 (0x0800), 172.31.3.252.67 > 172.31.3.11.68: BOOTP/DHCP, Reply, length 283

labsim/vlan-leak-evidence/after/capture-vif.txt

@@ -0,0 +1,6 @@
+12:52:14.639170 52:54:00:02:2e:b1 > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 342: 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 52:54:00:02:2e:b1, length 300
+12:52:14.640465 52:54:00:e5:95:a2 > 52:54:00:02:2e:b1, ethertype IPv4 (0x0800), length 325: 172.31.3.252.67 > 172.31.3.11.68: BOOTP/DHCP, Reply, length 283
+12:52:14.640845 52:54:00:e5:95:a2 > 52:54:00:02:2e:b1, ethertype IPv4 (0x0800), length 325: 172.31.3.252.67 > 172.31.3.11.68: BOOTP/DHCP, Reply, length 283
+12:52:14.642554 52:54:00:02:2e:b1 > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 342: 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 52:54:00:02:2e:b1, length 300
+12:52:14.642764 52:54:00:e5:95:a2 > 52:54:00:02:2e:b1, ethertype IPv4 (0x0800), length 325: 172.31.3.252.67 > 172.31.3.11.68: BOOTP/DHCP, Reply, length 283
+12:52:14.643055 52:54:00:e5:95:a2 > 52:54:00:02:2e:b1, ethertype IPv4 (0x0800), length 325: 172.31.3.252.67 > 172.31.3.11.68: BOOTP/DHCP, Reply, length 283

labsim/vlan-leak-evidence/after/client.txt

@@ -0,0 +1,4 @@
+udhcpc: started, v1.37.0
+udhcpc: broadcasting discover
+udhcpc: broadcasting select for 172.31.3.11, server 172.31.3.252
+udhcpc: lease of 172.31.3.11 obtained from 172.31.3.252, lease time 85374

labsim/vlan-leak-evidence/after/router-config.txt

@@ -0,0 +1,64 @@
+set high-availability vrrp group native address 172.31.1.1/24
+set high-availability vrrp group native hello-source-address '172.31.1.252'
+set high-availability vrrp group native interface 'bond0.1'
+set high-availability vrrp group native no-preempt
+set high-availability vrrp group native peer-address '172.31.1.253'
+set high-availability vrrp group native priority '200'
+set high-availability vrrp group native vrid '1'
+set high-availability vrrp group vlan2 address 172.31.2.1/24
+set high-availability vrrp group vlan2 hello-source-address '172.31.2.252'
+set high-availability vrrp group vlan2 interface 'bond0.2'
+set high-availability vrrp group vlan2 no-preempt
+set high-availability vrrp group vlan2 peer-address '172.31.2.253'
+set high-availability vrrp group vlan2 priority '200'
+set high-availability vrrp group vlan2 vrid '2'
+set high-availability vrrp group vlan3 address 172.31.3.1/24
+set high-availability vrrp group vlan3 hello-source-address '172.31.3.252'
+set high-availability vrrp group vlan3 interface 'bond0.3'
+set high-availability vrrp group vlan3 no-preempt
+set high-availability vrrp group vlan3 peer-address '172.31.3.253'
+set high-availability vrrp group vlan3 priority '200'
+set high-availability vrrp group vlan3 vrid '3'
+set high-availability vrrp group vlan9 address 172.31.9.1/24
+set high-availability vrrp group vlan9 hello-source-address '172.31.9.252'
+set high-availability vrrp group vlan9 interface 'bond0.9'
+set high-availability vrrp group vlan9 no-preempt
+set high-availability vrrp group vlan9 peer-address '172.31.9.253'
+set high-availability vrrp group vlan9 priority '200'
+set high-availability vrrp group vlan9 vrid '9'
+set high-availability vrrp group vlan10 address 172.31.10.1/23
+set high-availability vrrp group vlan10 hello-source-address '172.31.10.252'
+set high-availability vrrp group vlan10 interface 'bond0.10'
+set high-availability vrrp group vlan10 no-preempt
+set high-availability vrrp group vlan10 peer-address '172.31.10.253'
+set high-availability vrrp group vlan10 priority '200'
+set high-availability vrrp group vlan10 vrid '10'
+set high-availability vrrp group vlan200 address 172.31.200.1/24
+set high-availability vrrp group vlan200 hello-source-address '172.31.200.252'
+set high-availability vrrp group vlan200 interface 'bond0.200'
+set high-availability vrrp group vlan200 no-preempt
+set high-availability vrrp group vlan200 peer-address '172.31.200.253'
+set high-availability vrrp group vlan200 priority '200'
+set high-availability vrrp group vlan200 vrid '200'
+set interfaces bonding bond0 description 'api-batch-test'
+set interfaces bonding bond0 hash-policy 'layer2+3'
+set interfaces bonding bond0 lacp-rate 'fast'
+set interfaces bonding bond0 member interface 'eth0'
+set interfaces bonding bond0 member interface 'eth1'
+set interfaces bonding bond0 mode '802.3ad'
+set interfaces bonding bond0 vif 1 address '172.31.1.252/24'
+set interfaces bonding bond0 vif 1 description 'management'
+set interfaces bonding bond0 vif 2 address '172.31.2.252/24'
+set interfaces bonding bond0 vif 2 description 'k8s'
+set interfaces bonding bond0 vif 3 address '172.31.3.252/24'
+set interfaces bonding bond0 vif 3 description 'kvm'
+set interfaces bonding bond0 vif 9 address '172.31.9.252/24'
+set interfaces bonding bond0 vif 9 description 'private'
+set interfaces bonding bond0 vif 10 address '172.31.10.252/23'
+set interfaces bonding bond0 vif 10 description 'lot'
+set interfaces bonding bond0 vif 51 description 'WAN1 Vodafone-equivalent (sim ISP PPPoE)'
+set interfaces bonding bond0 vif 53 address 'dhcp'
+set interfaces bonding bond0 vif 53 description 'WAN3 10gig-equivalent (sim ISP DHCP)'
+set interfaces bonding bond0 vif 53 dhcp-options default-route-distance '210'
+set interfaces bonding bond0 vif 200 address '172.31.200.252/24'
+set interfaces bonding bond0 vif 200 description 'roomates'

labsim/vlan-leak-evidence/before/capture-parent.txt

@@ -0,0 +1,5 @@
+12:37:08.491910 52:54:00:02:2e:b1 > ff:ff:ff:ff:ff:ff, ethertype 802.1Q (0x8100), length 346: vlan 3, p 0, ethertype IPv4 (0x0800), 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 52:54:00:02:2e:b1, length 300
+12:37:08.492629 52:54:00:e5:95:a2 > 52:54:00:02:2e:b1, ethertype IPv4 (0x0800), length 325: 172.31.1.252.67 > 172.31.1.9.68: BOOTP/DHCP, Reply, length 283
+12:37:08.493628 52:54:00:e5:95:a2 > 52:54:00:02:2e:b1, ethertype 802.1Q (0x8100), length 329: vlan 3, p 0, ethertype IPv4 (0x0800), 172.31.3.252.67 > 172.31.3.11.68: BOOTP/DHCP, Reply, length 283
+12:37:08.495587 52:54:00:02:2e:b1 > ff:ff:ff:ff:ff:ff, ethertype 802.1Q (0x8100), length 346: vlan 3, p 0, ethertype IPv4 (0x0800), 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 52:54:00:02:2e:b1, length 300
+12:37:08.495946 52:54:00:e5:95:a2 > 52:54:00:02:2e:b1, ethertype 802.1Q (0x8100), length 329: vlan 3, p 0, ethertype IPv4 (0x0800), 172.31.3.252.67 > 172.31.3.11.68: BOOTP/DHCP, Reply, length 283

labsim/vlan-leak-evidence/before/capture-vif.txt

@@ -0,0 +1,4 @@
+12:37:08.491910 52:54:00:02:2e:b1 > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 342: 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 52:54:00:02:2e:b1, length 300
+12:37:08.493625 52:54:00:e5:95:a2 > 52:54:00:02:2e:b1, ethertype IPv4 (0x0800), length 325: 172.31.3.252.67 > 172.31.3.11.68: BOOTP/DHCP, Reply, length 283
+12:37:08.495587 52:54:00:02:2e:b1 > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 342: 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 52:54:00:02:2e:b1, length 300
+12:37:08.495944 52:54:00:e5:95:a2 > 52:54:00:02:2e:b1, ethertype IPv4 (0x0800), length 325: 172.31.3.252.67 > 172.31.3.11.68: BOOTP/DHCP, Reply, length 283

labsim/vlan-leak-evidence/before/client.txt

@@ -0,0 +1,4 @@
+udhcpc: started, v1.37.0
+udhcpc: broadcasting discover
+udhcpc: broadcasting select for 172.31.3.11, server 172.31.3.252
+udhcpc: lease of 172.31.3.11 obtained from 172.31.3.252, lease time 86280

labsim/vlan-leak-evidence/before/router-config.txt

@@ -0,0 +1,63 @@
+set high-availability vrrp group native address 172.31.1.1/24
+set high-availability vrrp group native hello-source-address '172.31.1.252'
+set high-availability vrrp group native interface 'bond0'
+set high-availability vrrp group native no-preempt
+set high-availability vrrp group native peer-address '172.31.1.253'
+set high-availability vrrp group native priority '200'
+set high-availability vrrp group native vrid '1'
+set high-availability vrrp group vlan2 address 172.31.2.1/24
+set high-availability vrrp group vlan2 hello-source-address '172.31.2.252'
+set high-availability vrrp group vlan2 interface 'bond0.2'
+set high-availability vrrp group vlan2 no-preempt
+set high-availability vrrp group vlan2 peer-address '172.31.2.253'
+set high-availability vrrp group vlan2 priority '200'
+set high-availability vrrp group vlan2 vrid '2'
+set high-availability vrrp group vlan3 address 172.31.3.1/24
+set high-availability vrrp group vlan3 hello-source-address '172.31.3.252'
+set high-availability vrrp group vlan3 interface 'bond0.3'
+set high-availability vrrp group vlan3 no-preempt
+set high-availability vrrp group vlan3 peer-address '172.31.3.253'
+set high-availability vrrp group vlan3 priority '200'
+set high-availability vrrp group vlan3 vrid '3'
+set high-availability vrrp group vlan9 address 172.31.9.1/24
+set high-availability vrrp group vlan9 hello-source-address '172.31.9.252'
+set high-availability vrrp group vlan9 interface 'bond0.9'
+set high-availability vrrp group vlan9 no-preempt
+set high-availability vrrp group vlan9 peer-address '172.31.9.253'
+set high-availability vrrp group vlan9 priority '200'
+set high-availability vrrp group vlan9 vrid '9'
+set high-availability vrrp group vlan10 address 172.31.10.1/23
+set high-availability vrrp group vlan10 hello-source-address '172.31.10.252'
+set high-availability vrrp group vlan10 interface 'bond0.10'
+set high-availability vrrp group vlan10 no-preempt
+set high-availability vrrp group vlan10 peer-address '172.31.10.253'
+set high-availability vrrp group vlan10 priority '200'
+set high-availability vrrp group vlan10 vrid '10'
+set high-availability vrrp group vlan200 address 172.31.200.1/24
+set high-availability vrrp group vlan200 hello-source-address '172.31.200.252'
+set high-availability vrrp group vlan200 interface 'bond0.200'
+set high-availability vrrp group vlan200 no-preempt
+set high-availability vrrp group vlan200 peer-address '172.31.200.253'
+set high-availability vrrp group vlan200 priority '200'
+set high-availability vrrp group vlan200 vrid '200'
+set interfaces bonding bond0 address '172.31.1.252/24'
+set interfaces bonding bond0 description 'api-batch-test'
+set interfaces bonding bond0 hash-policy 'layer2+3'
+set interfaces bonding bond0 lacp-rate 'fast'
+set interfaces bonding bond0 member interface 'eth0'
+set interfaces bonding bond0 member interface 'eth1'
+set interfaces bonding bond0 mode '802.3ad'
+set interfaces bonding bond0 vif 2 address '172.31.2.252/24'
+set interfaces bonding bond0 vif 2 description 'k8s'
+set interfaces bonding bond0 vif 3 address '172.31.3.252/24'
+set interfaces bonding bond0 vif 3 description 'kvm'
+set interfaces bonding bond0 vif 9 address '172.31.9.252/24'
+set interfaces bonding bond0 vif 9 description 'private'
+set interfaces bonding bond0 vif 10 address '172.31.10.252/23'
+set interfaces bonding bond0 vif 10 description 'lot'
+set interfaces bonding bond0 vif 51 description 'WAN1 Vodafone-equivalent (sim ISP PPPoE)'
+set interfaces bonding bond0 vif 53 address 'dhcp'
+set interfaces bonding bond0 vif 53 description 'WAN3 10gig-equivalent (sim ISP DHCP)'
+set interfaces bonding bond0 vif 53 dhcp-options default-route-distance '210'
+set interfaces bonding bond0 vif 200 address '172.31.200.252/24'
+set interfaces bonding bond0 vif 200 description 'roomates'

labsim/vlan1-move-monitor.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+# Timestamped liveness log for the Management VLAN during the bond0 -> bond0.1 move.
+#
+# The question this answers is not "did it work" but "for how long was it not
+# working, and what held the VIP while it was not". Both are invisible after the
+# fact: VRRP reconverges and leaves no trace of who was master during the gap.
+#
+#   ./vlan1-move-monitor.sh > /tmp/move.log &
+# Columns: time  VIP-ping  R1-ping  R2-ping  VIP-mac
+VIP="${VIP:-172.31.1.1}"; R1="${R1:-172.31.1.252}"; R2="${R2:-172.31.1.253}"
+p() { ping -c1 -W1 -n "$1" >/dev/null 2>&1 && echo up || echo DOWN; }
+while :; do
+  mac="$(ip neigh show "$VIP" 2>/dev/null | awk '{for(i=1;i<=NF;i++) if($i=="lladdr") print $(i+1)}')"
+  printf '%s  vip=%-4s r1=%-4s r2=%-4s vipmac=%s\n' \
+    "$(date +%H:%M:%S)" "$(p "$VIP")" "$(p "$R1")" "$(p "$R2")" "${mac:-none}"
+  sleep 1
+done

labsim/vlans.conf

@@ -12,10 +12,32 @@
 #   .10   the micro VM for this VLAN
 #   .254  VRRP VIP             (reserved, mirrors production)
 #
-# Format: vlan_id:name:sim_subnet_prefix:real_subnet(for reference)
+# Format: vlan_id:name:sim_subnet_prefix:real_subnet:[masklen]:[host_octet]
+#
+# masklen defaults to 24 and host_octet to 2. Both exist for VLAN 10, which is
+# the one VLAN that has to be a /23 here: every UniFi DHCP reservation lives in
+# LoT, and LoT spans 10.0.0.x AND 10.0.1.x, which a /24 cannot represent. With
+# /23 the mapping stays readable — 10.0.0.46 -> 172.31.10.46 and
+# 10.0.1.67 -> 172.31.11.67.
+#
+# LoT's host leg is .3 rather than .2 because 10.0.0.2 is a real reservation
+# (Hubitat) and would map straight onto the host's own address. .3 is free in
+# production and sits below the DHCP pool (which starts at .11), so it can
+# never be handed out.
 1:management:172.31.1:192.168.1.0/24
 2:k8s:172.31.2:192.168.8.0/23
 3:kvm:172.31.3:192.168.3.0/24
 9:private:172.31.9:10.0.9.0/23
-10:lot:172.31.10:10.0.0.0/23
+10:lot:172.31.10:10.0.0.0/23:23:3
 200:roomates:172.31.200:192.168.2.0/24
+
+# WAN transport VLANs, mirroring production. These exist so the sim can run a
+# fake ISP on each and the switch script's WAN health checks actually execute
+# instead of printing "this delta configures no WAN -- skipping". A cutover
+# attempt failed on the WAN with nothing having tested it, because the sim
+# modelled every LAN VLAN faithfully and omitted the WAN entirely.
+#
+# No host leg is wanted here (host_octet 0 means "skip"): the ISP VMs own these
+# segments, and a host address on a WAN transport VLAN would be a lie.
+51:wan1:172.31.51:vodafone-pppoe(VLAN 51):24:0
+53:wan3:172.31.53:10gig-dhcp(VLAN 53):24:0

labsim/wan-failover-evidence/README.md

@@ -0,0 +1,85 @@
+# WAN failover evidence
+
+Captured by `labsim/labsim-pppoe-ha-test.sh`. Each directory holds the state of
+both routers and the access concentrator at the end of one test.
+
+## The number that sizes GRACE
+
+`T4` destroys the master with `virsh destroy` — no LCP Terminate, no PADT, the
+router simply ceases — and times how long until the survivor holds a PPPoE
+session. Run across every policy VyOS can express, because Vodafone's is
+unknown:
+
+Two independent runs, so these describe the AC's behaviour rather than one-offs:
+
+| `session-control` | takeover | |
+|---|---|---|
+| `replace` | 26s / 26s | accel-ppp default; the new auth kills the old session |
+| **`deny`** | **148s / 141s** | the AC refuses the survivor until its own dead-peer timer frees the dead session |
+| `disable` | 21s / 20s | no single-session enforcement at all |
+
+`deny` is the only one that matters for sizing, and `GRACE=300` in
+`migration/vrrp-wan.conf` comes from it. Session polling during that run caught
+the mechanism directly: the destroyed router's session stayed in the AC's table
+while the survivor's dial attempts appeared and were rejected — twice — before
+one finally took.
+
+**Treat 148s as a floor, not a worst case.** These are idle 2-vCPU VMs, and the
+AC shares an OVS bridge with the routers, so `virsh destroy` removes the port
+and accel-ppp sees the peer physically vanish. A real BRAS reached over DSL
+never learns our router died; it waits out its own timers, which are longer and
+not ours to know.
+
+## How these numbers were nearly wrong
+
+Until 2026-09-06 the matrix set the policy with:
+
+```sh
+isp "vbash -c 'source /opt/vyatta/etc/functions/script-template; configure; \
+     set service pppoe-server session-control $mode; commit; save; exit'"
+```
+
+That form never starts a config session. `commit` fails with
+`Invalid command: [commit]` on stderr, which `isp()` discards — so all three
+iterations ran against the accel-ppp default while printing the mode they were
+supposedly testing. `show configuration commands | grep session-control` on the
+ISP VM came back empty after a full run. The matrix reported `deny` at 25s; the
+real figure is 148s, and `GRACE` was sized against the fiction.
+
+`isp_session_control()` now drives it from a real script file, reads the value
+back, and skips the iteration rather than measure the wrong policy. A harness
+that reports coverage it does not have is worse than one that reports a failure.
+
+## The other tests
+
+| | what it proves |
+|---|---|
+| `T0-baseline` | exactly one session, held by the VIP holder |
+| `T3-clean-failover` | `force-fault` moves `pppoe0` in 20–26s |
+| `T5-tengig-down` | 10 gig down → route falls to `pppoe0`, LAN back in 5s |
+| `T8-lease-expiry` | the guard hangs up a stale lease within ~5s |
+| `T11-no-peers-file` | a blessed box with no peers file does not restart-loop |
+| `T12-holdoff-keeps-session` | a 900s flap hold-off does **not** tear down a live session |
+
+`T12` exists because it did. `ppp_dial()` checked the hold-off and returned
+before renewing `/run/vrrp-wan/may-dial`; that lease is what `vrrp-wan-guard`
+expires, so tripping the damper stopped the renewal and the guard hung up
+`pppoe0` on the master ~80s later:
+
+```
+DIAL FLAP: >=6 attempts in 600s -- holding off 900s
+GUARD: lease stale (81s > 75s) -- hanging up pppoe0
+```
+
+A damper meant to suppress repeated *dials* was destroying an established
+session instead.
+
+## Reading `check_invariant`
+
+The invariant that matters is **at most one of our routers holds `pppoe0`**.
+The AC's session count is only a proxy for it, and only while the AC enforces
+single-session — under `disable` it does not, so a destroyed router's session
+lingers and the count reads 2 with exactly one live router dialled. That is
+reported as a `WARN`, not a failure. It is not silenced, because an orphaned
+session still occupies the single slot at a real ISP: it is exactly what made
+`deny` take 148s.

labsim/wan-failover-evidence/T0-baseline/state.txt

@@ -0,0 +1,31 @@
+=== 2026-09-06T00:27:16+01:00 ===
+--- AC sessions ---
+ ifname | username |       ip       | ip6 | ip6-dp |    calling-sid    | rate-limit | state  |  uptime  | rx-bytes | tx-bytes 
+--------+----------+----------------+-----+--------+-------------------+------------+--------+----------+----------+----------
+ ppp1   | simdsl   | 198.51.100.131 |     |        | 52:54:00:4e:0b:56 |            | active | 00:04:24 | 1.1 KiB  | 204 B
+--- 172.31.1.252 ---
+vip=172.31.1.1 holds_vip=no wan_disabled=yes wan_up=no ppp_up=no ppp_active=no may_dial=no lease_age=- dropin=yes role=backup
+Sep 05 23:07:43 apitest vrrp-wan[22667]: MASTER: dialling pppoe0
+Sep 05 23:08:14 apitest vrrp-wan[24120]: MASTER: dialling pppoe0
+-- Boot c5f23399239b468c8c8b752a4305c515 --
+Sep 05 23:13:04 apitest vrrp-wan[6261]: MASTER: dialling pppoe0
+Sep 05 23:13:04 apitest vrrp-wan[6413]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:13:08 apitest vrrp-wan[7122]: bond0.53 enable commit took 4s
+-- Boot 46727d256db344d6ad4b37c142272071 --
+Sep 05 23:18:31 apitest vrrp-wan[6258]: MASTER: dialling pppoe0
+Sep 05 23:18:31 apitest vrrp-wan[6411]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:18:36 apitest vrrp-wan[7038]: bond0.53 enable commit took 5s
+--- 172.31.1.253 ---
+vip=172.31.1.1 holds_vip=yes wan_disabled=no wan_up=yes ppp_up=yes ppp_active=yes may_dial=yes lease_age=19 dropin=yes role=master
+pppoe0           UNKNOWN        198.51.100.131 peer 198.51.100.1/32 
+default nhid 57 dev pppoe0 proto static metric 20 
+Sep 05 23:10:44 vyos vrrp-wan[221212]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:10:48 vyos vrrp-wan[221995]: bond0.53 enable commit took 4s
+-- Boot 1f635fc6900c4661b3ac6d016d63d293 --
+Sep 05 23:16:10 vyos vrrp-wan[7037]: MASTER: dialling pppoe0
+Sep 05 23:16:11 vyos vrrp-wan[7190]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:16:15 vyos vrrp-wan[7979]: bond0.53 enable commit took 4s
+-- Boot c0e38585d7354ad6ab018800c7f3f6be --
+Sep 05 23:22:54 vyos vrrp-wan[5970]: MASTER: dialling pppoe0
+Sep 05 23:22:54 vyos vrrp-wan[6126]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:22:59 vyos vrrp-wan[6915]: bond0.53 enable commit took 5s

labsim/wan-failover-evidence/T11-no-peers-file/state.txt

@@ -0,0 +1,26 @@
+=== 2026-09-06T00:29:55+01:00 ===
+--- AC sessions ---
+ ifname | username | ip | ip6 | ip6-dp | calling-sid | rate-limit | state | uptime | rx-bytes | tx-bytes 
+--------+----------+----+-----+--------+-------------+------------+-------+--------+----------+----------
+--- 172.31.1.252 ---
+vip=172.31.1.1 holds_vip=yes wan_disabled=no wan_up=no ppp_up=no ppp_active=yes may_dial=yes lease_age=1 dropin=yes role=master
+Sep 05 23:18:31 apitest vrrp-wan[6411]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:18:36 apitest vrrp-wan[7038]: bond0.53 enable commit took 5s
+-- Boot 68bb1e8d56b34d55a511a301c24270fe --
+Sep 05 23:27:40 apitest vrrp-wan[12502]: MASTER: dialling pppoe0
+Sep 05 23:27:40 apitest vrrp-wan[12654]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:27:45 apitest vrrp-wan[13361]: bond0.53 enable commit took 5s
+Sep 05 23:29:01 apitest vrrp-wan[16369]: GUARD: lease stale (200s > 75s; is vrrp-wan-reconcile.timer running?) -- hanging up pppoe0
+Sep 05 23:29:27 apitest vrrp-wan[17398]: MASTER: dialling pppoe0
+Sep 05 23:29:57 apitest vrrp-wan[18610]: MASTER: dialling pppoe0
+--- 172.31.1.253 ---
+vip=172.31.1.1 holds_vip=no wan_disabled=yes wan_up=no ppp_up=no ppp_active=no may_dial=no lease_age=- dropin=yes role=backup
+Sep 05 23:16:11 vyos vrrp-wan[7190]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:16:15 vyos vrrp-wan[7979]: bond0.53 enable commit took 4s
+-- Boot c0e38585d7354ad6ab018800c7f3f6be --
+Sep 05 23:22:54 vyos vrrp-wan[5970]: MASTER: dialling pppoe0
+Sep 05 23:22:54 vyos vrrp-wan[6126]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:22:59 vyos vrrp-wan[6915]: bond0.53 enable commit took 5s
+Sep 05 23:27:40 vyos vrrp-wan[16037]: not MASTER: hanging up pppoe0
+Sep 05 23:27:40 vyos vrrp-wan[16198]: not MASTER but bond0.53 enabled -> releasing
+Sep 05 23:27:47 vyos vrrp-wan[16840]: bond0.53 disable commit took 7s

labsim/wan-failover-evidence/T12-holdoff-keeps-session/state.txt

@@ -0,0 +1,29 @@
+=== 2026-09-06T00:31:55+01:00 ===
+--- AC sessions ---
+ ifname | username |       ip       | ip6 | ip6-dp |    calling-sid    | rate-limit | state  |  uptime  | rx-bytes | tx-bytes 
+--------+----------+----------------+-----+--------+-------------------+------------+--------+----------+----------+----------
+ ppp0   | simdsl   | 198.51.100.134 |     |        | 52:54:00:e5:95:a2 |            | active | 00:01:58 | 670 B    | 555 B
+--- 172.31.1.252 ---
+vip=172.31.1.1 holds_vip=yes wan_disabled=no wan_up=no ppp_up=yes ppp_active=yes may_dial=yes lease_age=21 dropin=yes role=master
+pppoe0           UNKNOWN        198.51.100.134 peer 198.51.100.1/32 
+default nhid 74 dev pppoe0 proto static metric 20 
+Sep 05 23:18:31 apitest vrrp-wan[6411]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:18:36 apitest vrrp-wan[7038]: bond0.53 enable commit took 5s
+-- Boot 68bb1e8d56b34d55a511a301c24270fe --
+Sep 05 23:27:40 apitest vrrp-wan[12502]: MASTER: dialling pppoe0
+Sep 05 23:27:40 apitest vrrp-wan[12654]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:27:45 apitest vrrp-wan[13361]: bond0.53 enable commit took 5s
+Sep 05 23:29:01 apitest vrrp-wan[16369]: GUARD: lease stale (200s > 75s; is vrrp-wan-reconcile.timer running?) -- hanging up pppoe0
+Sep 05 23:29:27 apitest vrrp-wan[17398]: MASTER: dialling pppoe0
+Sep 05 23:29:57 apitest vrrp-wan[18610]: MASTER: dialling pppoe0
+--- 172.31.1.253 ---
+vip=172.31.1.1 holds_vip=no wan_disabled=yes wan_up=no ppp_up=no ppp_active=no may_dial=no lease_age=- dropin=yes role=backup
+Sep 05 23:16:11 vyos vrrp-wan[7190]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:16:15 vyos vrrp-wan[7979]: bond0.53 enable commit took 4s
+-- Boot c0e38585d7354ad6ab018800c7f3f6be --
+Sep 05 23:22:54 vyos vrrp-wan[5970]: MASTER: dialling pppoe0
+Sep 05 23:22:54 vyos vrrp-wan[6126]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:22:59 vyos vrrp-wan[6915]: bond0.53 enable commit took 5s
+Sep 05 23:27:40 vyos vrrp-wan[16037]: not MASTER: hanging up pppoe0
+Sep 05 23:27:40 vyos vrrp-wan[16198]: not MASTER but bond0.53 enabled -> releasing
+Sep 05 23:27:47 vyos vrrp-wan[16840]: bond0.53 disable commit took 7s

labsim/wan-failover-evidence/T3-clean-failover/state.txt

@@ -0,0 +1,30 @@
+=== 2026-09-06T00:27:58+01:00 ===
+--- AC sessions ---
+ ifname | username |       ip       | ip6 | ip6-dp |    calling-sid    | rate-limit | state  |  uptime  | rx-bytes | tx-bytes 
+--------+----------+----------------+-----+--------+-------------------+------------+--------+----------+----------+----------
+ ppp0   | simdsl   | 198.51.100.132 |     |        | 52:54:00:e5:95:a2 |            | active | 00:00:18 | 514 B    | 204 B
+--- 172.31.1.252 ---
+vip=172.31.1.1 holds_vip=yes wan_disabled=no wan_up=yes ppp_up=yes ppp_active=yes may_dial=yes lease_age=7 dropin=yes role=master
+pppoe0           UNKNOWN        198.51.100.132 peer 198.51.100.1/32 
+default via 203.0.113.1 dev bond0.53 proto failover metric 1 
+Sep 05 23:13:04 apitest vrrp-wan[6413]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:13:08 apitest vrrp-wan[7122]: bond0.53 enable commit took 4s
+-- Boot 46727d256db344d6ad4b37c142272071 --
+Sep 05 23:18:31 apitest vrrp-wan[6258]: MASTER: dialling pppoe0
+Sep 05 23:18:31 apitest vrrp-wan[6411]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:18:36 apitest vrrp-wan[7038]: bond0.53 enable commit took 5s
+-- Boot 68bb1e8d56b34d55a511a301c24270fe --
+Sep 05 23:27:40 apitest vrrp-wan[12502]: MASTER: dialling pppoe0
+Sep 05 23:27:40 apitest vrrp-wan[12654]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:27:45 apitest vrrp-wan[13361]: bond0.53 enable commit took 5s
+--- 172.31.1.253 ---
+vip=172.31.1.1 holds_vip=no wan_disabled=yes wan_up=no ppp_up=no ppp_active=no may_dial=no lease_age=- dropin=yes role=backup
+Sep 05 23:16:11 vyos vrrp-wan[7190]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:16:15 vyos vrrp-wan[7979]: bond0.53 enable commit took 4s
+-- Boot c0e38585d7354ad6ab018800c7f3f6be --
+Sep 05 23:22:54 vyos vrrp-wan[5970]: MASTER: dialling pppoe0
+Sep 05 23:22:54 vyos vrrp-wan[6126]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:22:59 vyos vrrp-wan[6915]: bond0.53 enable commit took 5s
+Sep 05 23:27:40 vyos vrrp-wan[16037]: not MASTER: hanging up pppoe0
+Sep 05 23:27:40 vyos vrrp-wan[16198]: not MASTER but bond0.53 enabled -> releasing
+Sep 05 23:27:47 vyos vrrp-wan[16840]: bond0.53 disable commit took 7s

labsim/wan-failover-evidence/T4-hard-failover-deny/state.txt

@@ -0,0 +1,19 @@
+=== 2026-09-06T00:37:11+01:00 ===
+--- AC sessions ---
+ ifname | username |       ip       | ip6 | ip6-dp |    calling-sid    | rate-limit | state  |  uptime  | rx-bytes | tx-bytes 
+--------+----------+----------------+-----+--------+-------------------+------------+--------+----------+----------+----------
+ ppp0   | simdsl   | 198.51.100.136 |     |        | 52:54:00:e5:95:a2 |            | active | 00:00:13 | 438 B    | 204 B
+--- 172.31.1.252 ---
+vip=172.31.1.1 holds_vip=yes wan_disabled=no wan_up=yes ppp_up=yes ppp_active=yes may_dial=yes lease_age=26 dropin=yes role=master
+pppoe0           UNKNOWN        198.51.100.136 peer 198.51.100.1/32 
+default via 203.0.113.1 dev bond0.53 proto failover metric 1 
+Sep 05 23:27:40 apitest vrrp-wan[12654]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:27:45 apitest vrrp-wan[13361]: bond0.53 enable commit took 5s
+Sep 05 23:29:01 apitest vrrp-wan[16369]: GUARD: lease stale (200s > 75s; is vrrp-wan-reconcile.timer running?) -- hanging up pppoe0
+Sep 05 23:29:27 apitest vrrp-wan[17398]: MASTER: dialling pppoe0
+Sep 05 23:29:57 apitest vrrp-wan[18610]: MASTER: dialling pppoe0
+-- Boot 6efc3c9ba47f455e9668454ee6c2fc37 --
+Sep 05 23:34:48 apitest vrrp-wan[6266]: MASTER: dialling pppoe0
+Sep 05 23:34:49 apitest vrrp-wan[6422]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:34:54 apitest vrrp-wan[7130]: bond0.53 enable commit took 5s
+--- 172.31.1.253 ---

labsim/wan-failover-evidence/T4-hard-failover-disable/state.txt

@@ -0,0 +1,20 @@
+=== 2026-09-06T00:39:29+01:00 ===
+--- AC sessions ---
+ ifname | username |       ip       | ip6 | ip6-dp |    calling-sid    | rate-limit | state  |  uptime  | rx-bytes | tx-bytes 
+--------+----------+----------------+-----+--------+-------------------+------------+--------+----------+----------+----------
+ ppp0   | simdsl   | 198.51.100.136 |     |        | 52:54:00:e5:95:a2 |            | active | 00:02:31 | 438 B    | 204 B    
+ ppp1   | simdsl   | 198.51.100.137 |     |        | 52:54:00:4e:0b:56 |            | active | 00:00:26 | 1.0 KiB  | 204 B
+--- 172.31.1.252 ---
+--- 172.31.1.253 ---
+vip=172.31.1.1 holds_vip=yes wan_disabled=no wan_up=yes ppp_up=yes ppp_active=yes may_dial=yes lease_age=5 dropin=yes role=master
+pppoe0           UNKNOWN        198.51.100.137 peer 198.51.100.1/32 
+default nhid 60 dev pppoe0 proto static metric 20 
+Sep 05 23:27:40 vyos vrrp-wan[16198]: not MASTER but bond0.53 enabled -> releasing
+Sep 05 23:27:47 vyos vrrp-wan[16840]: bond0.53 disable commit took 7s
+Sep 05 23:32:26 vyos vrrp-wan[23806]: MASTER: dialling pppoe0
+Sep 05 23:32:26 vyos vrrp-wan[23956]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:32:31 vyos vrrp-wan[24749]: bond0.53 enable commit took 5s
+-- Boot 4b0355878444477fb92738339f85843d --
+Sep 05 23:39:03 vyos vrrp-wan[5966]: MASTER: dialling pppoe0
+Sep 05 23:39:04 vyos vrrp-wan[6120]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:39:09 vyos vrrp-wan[6914]: bond0.53 enable commit took 5s

labsim/wan-failover-evidence/T4-hard-failover-replace/state.txt

@@ -0,0 +1,18 @@
+=== 2026-09-06T00:32:54+01:00 ===
+--- AC sessions ---
+ ifname | username |       ip       | ip6 | ip6-dp |    calling-sid    | rate-limit | state  |  uptime  | rx-bytes | tx-bytes 
+--------+----------+----------------+-----+--------+-------------------+------------+--------+----------+----------+----------
+ ppp0   | simdsl   | 198.51.100.135 |     |        | 52:54:00:4e:0b:56 |            | active | 00:00:30 | 438 B    | 204 B
+--- 172.31.1.252 ---
+--- 172.31.1.253 ---
+vip=172.31.1.1 holds_vip=yes wan_disabled=no wan_up=yes ppp_up=yes ppp_active=yes may_dial=yes lease_age=19 dropin=yes role=master
+pppoe0           UNKNOWN        198.51.100.135 peer 198.51.100.1/32 
+default nhid 77 dev pppoe0 proto static metric 20 
+Sep 05 23:22:54 vyos vrrp-wan[6126]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:22:59 vyos vrrp-wan[6915]: bond0.53 enable commit took 5s
+Sep 05 23:27:40 vyos vrrp-wan[16037]: not MASTER: hanging up pppoe0
+Sep 05 23:27:40 vyos vrrp-wan[16198]: not MASTER but bond0.53 enabled -> releasing
+Sep 05 23:27:47 vyos vrrp-wan[16840]: bond0.53 disable commit took 7s
+Sep 05 23:32:26 vyos vrrp-wan[23806]: MASTER: dialling pppoe0
+Sep 05 23:32:26 vyos vrrp-wan[23956]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:32:31 vyos vrrp-wan[24749]: bond0.53 enable commit took 5s

labsim/wan-failover-evidence/T5-tengig-down/state.txt

@@ -0,0 +1,30 @@
+=== 2026-09-06T00:28:31+01:00 ===
+--- AC sessions ---
+ ifname | username |       ip       | ip6 | ip6-dp |    calling-sid    | rate-limit | state  |  uptime  | rx-bytes | tx-bytes 
+--------+----------+----------------+-----+--------+-------------------+------------+--------+----------+----------+----------
+ ppp0   | simdsl   | 198.51.100.132 |     |        | 52:54:00:e5:95:a2 |            | active | 00:00:52 | 682 B    | 372 B
+--- 172.31.1.252 ---
+vip=172.31.1.1 holds_vip=yes wan_disabled=no wan_up=yes ppp_up=yes ppp_active=yes may_dial=yes lease_age=7 dropin=yes role=master
+pppoe0           UNKNOWN        198.51.100.132 peer 198.51.100.1/32 
+default nhid 58 dev pppoe0 proto static metric 20 
+Sep 05 23:13:04 apitest vrrp-wan[6413]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:13:08 apitest vrrp-wan[7122]: bond0.53 enable commit took 4s
+-- Boot 46727d256db344d6ad4b37c142272071 --
+Sep 05 23:18:31 apitest vrrp-wan[6258]: MASTER: dialling pppoe0
+Sep 05 23:18:31 apitest vrrp-wan[6411]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:18:36 apitest vrrp-wan[7038]: bond0.53 enable commit took 5s
+-- Boot 68bb1e8d56b34d55a511a301c24270fe --
+Sep 05 23:27:40 apitest vrrp-wan[12502]: MASTER: dialling pppoe0
+Sep 05 23:27:40 apitest vrrp-wan[12654]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:27:45 apitest vrrp-wan[13361]: bond0.53 enable commit took 5s
+--- 172.31.1.253 ---
+vip=172.31.1.1 holds_vip=no wan_disabled=yes wan_up=no ppp_up=no ppp_active=no may_dial=no lease_age=- dropin=yes role=backup
+Sep 05 23:16:11 vyos vrrp-wan[7190]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:16:15 vyos vrrp-wan[7979]: bond0.53 enable commit took 4s
+-- Boot c0e38585d7354ad6ab018800c7f3f6be --
+Sep 05 23:22:54 vyos vrrp-wan[5970]: MASTER: dialling pppoe0
+Sep 05 23:22:54 vyos vrrp-wan[6126]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:22:59 vyos vrrp-wan[6915]: bond0.53 enable commit took 5s
+Sep 05 23:27:40 vyos vrrp-wan[16037]: not MASTER: hanging up pppoe0
+Sep 05 23:27:40 vyos vrrp-wan[16198]: not MASTER but bond0.53 enabled -> releasing
+Sep 05 23:27:47 vyos vrrp-wan[16840]: bond0.53 disable commit took 7s

labsim/wan-failover-evidence/T8-lease-expiry/state.txt

@@ -0,0 +1,27 @@
+=== 2026-09-06T00:29:16+01:00 ===
+--- AC sessions ---
+ ifname | username | ip | ip6 | ip6-dp | calling-sid | rate-limit | state | uptime | rx-bytes | tx-bytes 
+--------+----------+----+-----+--------+-------------+------------+-------+--------+----------+----------
+--- 172.31.1.252 ---
+vip=172.31.1.1 holds_vip=yes wan_disabled=no wan_up=no ppp_up=no ppp_active=no may_dial=no lease_age=- dropin=yes role=master
+Sep 05 23:13:08 apitest vrrp-wan[7122]: bond0.53 enable commit took 4s
+-- Boot 46727d256db344d6ad4b37c142272071 --
+Sep 05 23:18:31 apitest vrrp-wan[6258]: MASTER: dialling pppoe0
+Sep 05 23:18:31 apitest vrrp-wan[6411]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:18:36 apitest vrrp-wan[7038]: bond0.53 enable commit took 5s
+-- Boot 68bb1e8d56b34d55a511a301c24270fe --
+Sep 05 23:27:40 apitest vrrp-wan[12502]: MASTER: dialling pppoe0
+Sep 05 23:27:40 apitest vrrp-wan[12654]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:27:45 apitest vrrp-wan[13361]: bond0.53 enable commit took 5s
+Sep 05 23:29:01 apitest vrrp-wan[16369]: GUARD: lease stale (200s > 75s; is vrrp-wan-reconcile.timer running?) -- hanging up pppoe0
+--- 172.31.1.253 ---
+vip=172.31.1.1 holds_vip=no wan_disabled=yes wan_up=no ppp_up=no ppp_active=no may_dial=no lease_age=- dropin=yes role=backup
+Sep 05 23:16:11 vyos vrrp-wan[7190]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:16:15 vyos vrrp-wan[7979]: bond0.53 enable commit took 4s
+-- Boot c0e38585d7354ad6ab018800c7f3f6be --
+Sep 05 23:22:54 vyos vrrp-wan[5970]: MASTER: dialling pppoe0
+Sep 05 23:22:54 vyos vrrp-wan[6126]: MASTER with bond0.53 disabled -> enabling
+Sep 05 23:22:59 vyos vrrp-wan[6915]: bond0.53 enable commit took 5s
+Sep 05 23:27:40 vyos vrrp-wan[16037]: not MASTER: hanging up pppoe0
+Sep 05 23:27:40 vyos vrrp-wan[16198]: not MASTER but bond0.53 enabled -> releasing
+Sep 05 23:27:47 vyos vrrp-wan[16840]: bond0.53 disable commit took 7s

migration/.gitignore

@@ -0,0 +1,4 @@
+# Raw UniFi export: contains WiFi passphrases (wlanconf) and controller auth
+# material (setting). The inventory is regenerable — never commit it.
+export/
+__pycache__/

migration/CUTOVER.md

@@ -0,0 +1,209 @@
+# Cutover runbook — USG to VyOS
+
+**Print this.** During the cutover there is no internet, so there is no
+assistant and no web search. Everything you need is on this page and on the
+boxes themselves.
+
+## Use these addresses. Not the other ones.
+
+| | use this | do NOT use |
+|---|---|---|
+| vyos001 (MASTER) | **`10.0.1.252`** | ~~192.168.8.143~~ |
+| vyos002 (BACKUP) | **`10.0.1.253`** | ~~192.168.8.144~~ |
+
+`ssh vyos@10.0.1.252` — by IP, not by name.
+
+**The `192.168.8.x` addresses stop working the instant the USG is unplugged.**
+That is not a maybe. Your workstation is on LoT (`10.0.0.210/23`) and reaching
+`192.168.8.x` requires routing *through the USG*:
+
+```
+ip route get 192.168.8.143  ->  via 10.0.0.1     <- the USG. Gone.
+ip route get 10.0.1.252     ->  dev lanbr0       <- same L2. Survives.
+```
+
+`10.0.1.252` and `.253` are on the LoT VLAN, the same broadcast domain as your
+workstation, so they need no gateway at all. They are the only remote path that
+survives the cutover.
+
+**Between unplugging the USG and finishing the switch there is no inter-VLAN
+routing.** In that window:
+
+- the **JetKVMs are unreachable** from your workstation (they are on Management
+  and kvm) — they are *not* a fallback during the gap
+- **Tailscale is down** with the internet
+- your workstation keeps `10.0.0.210` (86400s lease) and can still resolve via
+  `10.0.0.194`, which is also link-scope
+
+If LoT SSH fails, the next step is physical console, not the network.
+
+| | |
+|---|---|
+| JetKVMs (after routing is restored) | `192.168.1.28`, `192.168.1.29`, `192.168.3.6` |
+| Switch script | `/config/vyos-unifi-switch` on each box |
+| Peer link | `eth3` ↔ `eth3` direct cable, 2.5 GbE, `10.255.255.0/30` — conntrack state sync |
+| Login | user `vyos` |
+
+---
+
+## If something is wrong, do this
+
+```
+sudo /config/vyos-unifi-switch unifi
+```
+
+Then reconnect the USG. That command runs no health checks, asks nothing and
+cannot refuse. It restores a byte-exact copy of the configuration the box had
+before the cutover — verified by diff, not by assumption.
+
+**You do not have to be quick.** If you do nothing at all after
+`vyos-unifi-switch vyos`, the box reverts by itself within 10 minutes. Verified:
+config returns to the previous state and the box does **not** reboot
+(`uptime` and boot-id unchanged across an auto-revert).
+
+---
+
+## What has actually been tested
+
+Proven on the labsim router (same VyOS version, isolated OVS bridge with no
+physical NIC), by loading **vyos001's real running config** and applying the
+**real production delta**:
+
+- All 317 commands accepted, and the whole delta **commits** (`COMMIT OK`).
+- `unifi` mode restores the previous config **byte-exact** (diff clean).
+- Auto-revert fires when the commit is not confirmed: config returns to the
+  saved state and the box does **not** reboot — `uptime` and boot-id unchanged
+  across the revert.
+- Failed health checks trigger an immediate revert rather than waiting out the
+  timer.
+
+Two bugs were found this way and would each have failed the entire switch,
+since the delta commits as one unit: `bond0.51` did not exist for PPPoE to
+reference, and `translation port` rejects a port list.
+
+**Not tested, and untestable in advance:**
+
+- **PPPoE.** The line permits one session and the USG holds it. The first real
+  attempt is during the cutover.
+- **The commit on the real boxes.** The rehearsal ran with vyos001's `eth2` and
+  `eth3` stanzas stripped, because the sim VM has only two NICs. Those are
+  plain interface configs that already work on the real hardware, but they were
+  not part of what committed.
+
+## Before you unplug anything
+
+1. Tether your workstation to your phone if you want the assistant available.
+   Cutting the USG cuts your internet, not your LAN.
+2. On **both** boxes, confirm the machinery is present:
+   ```
+   sudo /config/vyos-unifi-switch status
+   ls -la /config/modes/          # unifi.boot + to-vyos.commands
+   ls -la /config/wan-secrets     # must be 0600
+   ```
+   `status` must report `mode: unifi`. If `unifi.boot` is missing, **stop** —
+   there is no way back without it.
+3. Confirm the revert action is `reload`, not `reboot`:
+   ```
+   show configuration commands | match commit-confirm
+   ```
+   Must show `action 'reload'`. Without it a failed switch **reboots** the
+   firewall instead of reverting it. The switch script refuses to run if this
+   is missing, but check anyway.
+
+## The cutover
+
+0. **Open both SSH sessions BEFORE you unplug anything**, and leave them open:
+   ```
+   ssh vyos@10.0.1.253      # vyos002, BACKUP
+   ssh vyos@10.0.1.252      # vyos001, MASTER
+   ```
+   If either will not connect, stop. Do not unplug the USG.
+
+1. **Physically disconnect the USG.** Not just powered off — disconnected. The
+   switch script refuses to run while anything still answers on a gateway
+   address, because two devices on `.1` is the worst available outcome.
+   You cannot switch first and unplug after, for exactly that reason.
+
+2. In the **vyos002 (BACKUP)** session, first:
+   ```
+   sudo /config/vyos-unifi-switch vyos
+   ```
+3. Watch the health checks. They cover PPPoE, the default route, kea, the DNS
+   forwarder and reachability. On failure the script reverts immediately and
+   tells you so.
+4. If vyos002 came up clean, repeat on **vyos001 (MASTER)**.
+5. Check a real client: does it get an address, and is it the *same* address as
+   before? Every active client has a reservation, so it should be.
+
+## What will probably go wrong first
+
+**The WAN.** There are two, and they behave differently:
+
+| | line | VLAN | transport | notes |
+|---|---|---|---|---|
+| WAN2 | 10 gig ISP | **53** | DHCP, public `87.192.101.48/21` | primary, distance 1 |
+| WAN1 | Vodafone | **51** | PPPoE, ~900/700 Mbit | failover, distance 10 |
+
+VyOS clones the USG's WAN2 MAC (`f0:9f:c2:12:9b:4f`) on `bond0.53`, which is how
+it keeps the existing public lease rather than asking for a new one.
+
+**Both boxes carry the identical WAN and NAT config.** vyos002's WAN interfaces
+are simply held administratively down, so the cloned MAC is never live on two
+boxes at once. To move the internet path to vyos002:
+
+```
+configure
+delete interfaces bonding bond0 vif 53 disable
+delete interfaces pppoe pppoe0 disable
+commit; save
+```
+
+Two lines. Do it only when vyos001 is genuinely down or disconnected — two boxes
+holding that MAC at once is exactly what the disable prevents.
+
+PPPoE is no longer an unknown: it was proven on the USG before cutover
+(`pppoe0` came up with `90.241.226.213`, MTU 1492). What remains untested is
+VyOS dialling it, and whether the ISP hands the same lease to the cloned MAC.
+
+If the WAN check fails:
+
+```
+show interfaces pppoe pppoe0
+sudo journalctl -u ppp@pppoe0 -n 50 --no-pager
+```
+
+Check the credential in `/config/wan-secrets` and that VLAN 51 actually reaches
+the box. If it will not come up, run `vyos-unifi-switch unifi`, reconnect the
+USG, and debug with the internet back on.
+
+## Things that are true and easy to forget
+
+- **WiFi keeps working, but through VyOS.** The SSIDs stay in UniFi and the APs
+  are untouched, but 37 of 83 active clients are wireless and every one is on
+  LoT — they get their addresses from VyOS now.
+- **DHCP leases last 24h (86400s).** A device that does not renew promptly keeps
+  its old address for a while. That is fine, not a symptom.
+- **The firewalls resolve via `8.8.8.8` / `8.8.4.4`** — matching the DNS the USG
+  used on its WAN. This means their own name resolution now depends on the
+  *internet* being up, so between unplugging the USG and PPPoE establishing,
+  the boxes have no DNS at all. That is expected and harmless: they only need
+  DNS for NTP hostnames, and the switch's own health checks use it precisely to
+  prove the WAN came up. Nothing in the switch itself resolves a name.
+- Internal `ad.itaz.eu` names still resolve through Google, because that zone is
+  published publicly with private addresses in it (`nas001` → `10.0.0.194`,
+  `kvm-macstudio1` → `192.168.3.8`). Convenient here; worth knowing it is public.
+- **The USG was a DNS resolver** for every VLAN except LoT. VyOS now runs
+  `dns forwarding` in its place. If names stop resolving but IPs still work,
+  that is where to look.
+- **`eth2` and `bond0.2` are both in `192.168.8.0/23`.** It works, but if you
+  see odd source-address behaviour on the management NIC, that is why.
+
+## Afterwards
+
+Once it has been stable for a day:
+
+- Re-run `migration/unifi-export.py` — the UniFi controller is no longer the
+  source of truth for DHCP, and the export will drift.
+- The VPN rules (ESP, UDP 500/4500) are carried over but the VPN itself still
+  terminated on the USG. Decide whether it moves.
+- `labsim` still holds a deliberate `kvm→k8s` drop rule from earlier testing.

migration/MANAGEMENT-VLAN-TAGGED.md

@@ -0,0 +1,137 @@
+# Moving Management onto a tagged VLAN
+
+Rehearsed end to end in labsim on 2026-09-02. This is the fix for kea serving
+addresses from the wrong VLAN's pool.
+
+## Why
+
+ISC Kea [#1117](https://gitlab.isc.org/isc-projects/kea/-/issues/1117): with
+`dhcp-socket-type: raw`, a frame tagged for a sub-interface is **also** delivered
+to the parent's `AF_PACKET` socket. If the parent serves a subnet, kea answers
+from it too. Ours does — Management is the native/untagged VLAN on `bond0` while
+VLANs 2/3/9/10/200 are sub-interfaces of that same bond — so one DISCOVER on
+VLAN 3 produces two OFFERs and the *client* decides which to keep:
+
+```
+bond0.3 :  192.168.3.14  correct
+bond0   :  192.168.1.28  UNTAGGED, Management pool, wrong
+```
+
+The fix is to leave **no subnet on the parent**: every VLAN tagged, Management
+included, moved from `bond0` to `bond0.1`.
+
+Confirmed in labsim across all six LAN VLANs: fails before, passes after.
+`labsim/labsim-vlan-leak-test.sh` is the test; evidence in
+`labsim/vlan-leak-evidence/`.
+
+## What must change together
+
+Per router:
+
+| | from | to |
+|---|---|---|
+| address | `interfaces bonding bond0 address` | `interfaces bonding bond0 vif 1 address` |
+| firewall | `interface-group LAN interface bond0` | `... interface bond0.1` |
+| VRRP | `vrrp group native interface bond0` | `... interface bond0.1` |
+| kea | — | **restart it** (see traps) |
+
+On the switch: Native VLAN = **None** on the trunk to that firewall, with VLAN 1
+added to the tagged set.
+
+## The ordering constraint
+
+**There is no overlap state.** An 802.1Q port always egresses its native VLAN
+untagged, so while VLAN 1 is native the router can *send* tagged VLAN 1 but can
+never *receive* it. Verified: a tagged VLAN 1 ARP sent from the switch arrived on
+`bond0` untagged and never on `bond0.1`. Configuring "native VLAN 1 **and** VLAN 1
+tagged" as a make-before-break does not work; the switch and router changes for a
+given firewall are strictly simultaneous, and that router loses Management in
+between.
+
+What makes this safe anyway: **tagged and untagged Management coexist on the
+same VLAN.** One VLAN is one broadcast domain no matter how each port tags it, so
+the firewalls can be converted one at a time — verified with the primary untagged
+and the secondary already tagged, both reachable, VIP up, VLAN 1 clients fine.
+
+Access ports are untouched throughout. The UniFi controller at 192.168.1.5 and
+your workstation are on access ports and never traverse the firewall trunks, so
+you keep the controller you are making the change from. Only the router being
+converted goes dark, and only until its own config lands.
+
+## Procedure
+
+Do the **backup** router first, then fail the VIPs over and do the other. You
+need console (JetKVM) on the router being converted — its Management SSH dies the
+moment the switch port changes.
+
+For each router in turn:
+
+1. Confirm the *other* router is MASTER and healthy:
+   `show vrrp` and `sudo /config/vrrp-wan-health; echo $?` (must be 0).
+2. Start the monitor from a workstation on an access port:
+   `labsim/vlan1-move-monitor.sh` (edit the three addresses for production).
+3. UniFi: on this firewall's trunk ports, Native VLAN → None, VLAN 1 → tagged.
+   This router's Management drops now.
+4. Over the console, in one commit:
+   ```
+   set interfaces bonding bond0 vif 1 address '192.168.1.252/24'   # .253 on vyos002
+   set interfaces bonding bond0 vif 1 description 'management'
+   delete interfaces bonding bond0 address
+   set firewall group interface-group LAN interface 'bond0.1'
+   delete firewall group interface-group LAN interface 'bond0'
+   set high-availability vrrp group native interface 'bond0.1'
+   commit
+   save
+   ```
+5. `sudo systemctl restart isc-kea-dhcp4-server` — see traps.
+6. Verify: Management SSH back, `show vrrp` shows `native` on `bond0.1`, and the
+   leak test passes.
+
+Then fail back if the VIPs moved (below), and repeat for the other router.
+
+### Measured windows (labsim)
+
+| | |
+|---|---|
+| this router's own Management unreachable | ~27 s (the console apply) |
+| VIP `.1` unreachable, peer already converted | **0 s** |
+| VIP `.1` unreachable, converting the current MASTER | ~6 s (VRRP failover) |
+| VIP unreachable if you convert both routers before the switch | **5 min 30 s** |
+
+That last row is the failure mode to avoid: with both routers untagged and the
+trunks already changed, the VIP is a black hole and **the healthy BACKUP does not
+take over**. Its `native` group stays BACKUP because the *other* VLANs still hear
+the master, and the sync group holds them together. Redundancy does not help you
+here; only ordering does.
+
+## Traps
+
+- **Restart kea.** VyOS does not restart it for an interface address change, so
+  it keeps a raw socket bound with the old address and keeps emitting the wrong
+  offers. The first post-fix test in the sim failed for this reason alone and
+  looked exactly like the fix not working.
+- **`interface-group LAN`.** Moving the address without moving the group means
+  Management falls outside the group, and with default-deny that is every
+  management session and all VLAN 1 inter-VLAN routing, gone on commit — on a
+  router you reach through itself. Use `commit-confirm` if you are not on console.
+- **The VIPs may move, and `no-preempt` keeps them moved.** Converting a router
+  restarts keepalived and re-initialises *every* group, not just `native`. In one
+  rehearsal the priority-100 secondary took all six VIPs and held them while the
+  priority-200 primary sat at BACKUP; in another the restart was quick enough that
+  nothing moved. It is non-deterministic — check afterwards, every time.
+  Fail back with `restart vrrp` **on the router currently holding them**.
+- **Duplicate delivery does not stop**, and should not be read as failure. #1117
+  only promises there is no longer a subnet on the parent to match. Expect two
+  identical replies per DISCOVER, both from the correct pool.
+- **Both firewalls' trunks must end up the same.** If UniFi shares one port
+  profile between them, changing it converts both at once and you get the 5m30s
+  row above. Check before you start; use per-port overrides if it does.
+
+## Not covered by the rehearsal
+
+- Whether UniFi's port profile can express "no native VLAN" the way OVS can, and
+  whether the two firewalls share a profile. Unverified — check on the controller.
+- Why the JetKVM consoles specifically accepted the wrong OFFER when a VLAN 3
+  access port should not receive an untagged VLAN 1 frame at all. Their port
+  profile likely passes VLAN 1 untagged. Worth confirming, though it does not
+  change the fix.

migration/PPPOE-HA.md

@@ -0,0 +1,360 @@
+# PPPoE high availability
+
+Proven in labsim. **Deployed to production 2026-09-06** — mechanism on both
+routers, `pppoe0 disable` removed from vyos002, vyos002 out of FAULT and in
+BACKUP, Pulumi model merged, and a controlled failover drill passed
+(takeover 52s, failback 36s). `vyos:verify` reports both routers in sync.
+
+## What it does
+
+One consumer ISP account, two routers. The 10 gig lease is bound to a cloned MAC
+(`f0:9f:c2:12:9b:4f`, the retired USG's) and the Vodafone line to a single
+credential, so neither may be live on both boxes. The WAN follows VRRP
+mastership — but the two halves use different control planes, and that is the
+whole design:
+
+| | plane | why |
+|---|---|---|
+| `bond0.53` (10 gig) | VyOS **config** (`disable`) | only config can move a MAC |
+| `pppoe0` (Vodafone) | **systemd** unit gate | see below |
+
+## Why PPPoE cannot live on the config plane
+
+`interfaces_pppoe.py` treats `disable` and `delete` identically: both **unlink
+`/etc/ppp/peers/pppoe0`**, call `PPPoEIf.remove()` (withdrawing the FRR default
+route) and stop the unit. That path is pppd's own options file
+(`ExecStart=/usr/sbin/pppd call %I`), so the resting state destroyed exactly what
+the promotion path needed. `ppp@pppoe0` then restart-looped against the missing
+file — 47 restarts observed, zero sessions at the access concentrator — and
+never tripped systemd's limiter, because `RestartSec=5s` against the default
+10s/5-burst window is only two restarts per interval.
+
+It also made op-mode `connect interface pppoe0` unusable (it refuses without the
+peers file), and put every failover behind a priority-322 commit where one
+unrelated invalid node fails the whole thing.
+
+## The gate
+
+`pppoe0` is configured identically and **enabled on both** routers, so the peers
+file always exists. Dialling is gated by
+`/etc/systemd/system/ppp@pppoe0.service.d/10-vrrp-wan-gate.conf`:
+
+```ini
+ConditionPathExists=/run/vrrp-wan/may-dial
+ConditionPathExists=/etc/ppp/peers/pppoe0
+StartLimitIntervalSec=600
+StartLimitBurst=6
+```
+
+`/run` is tmpfs, so the gate is shut at boot and neither box can dial before VRRP
+has decided. **This is load-bearing, not a nicety:** with the node enabled,
+`interfaces_pppoe.py` restarts ppp on *every* commit touching the pppoe subtree
+when the daemon is not running — so the backup actively tries to dial whenever
+anything commits (`pulumi up`, a hand commit, the boot-time config load). The
+gate is the only thing making that a no-op, which is why `vrrp-wan-reconcile`
+**refuses to bless a box whose drop-in is missing**: `/etc` is per-image, so a
+VyOS upgrade silently removes the protection, and failing closed turns that into
+"PPPoE never dials" rather than "both routers dial".
+
+`may-dial` is a **lease, not a flag**. `ConditionPathExists` is evaluated at
+start only — it can prevent a dial, never revoke one. `vrrp-wan-reconcile`
+renews it every 30s; `vrrp-wan-guard` runs every 5s and only ever revokes, on
+either "I do not hold the VIP" or "the lease is stale".
+
+## Measured in labsim
+
+| | |
+|---|---|
+| Clean failover (`force-fault`) | `pppoe0` moves in **20-26s**, reproducible |
+| 10 gig down → PPPoE | route falls to `pppoe0`; LAN back online in **5s** |
+| Stale lease | guard hangs up within ~5s |
+| Missing peers file | `NRestarts=0` — no loop |
+| Flap holdoff vs live session | session survives a forged 900s holdoff |
+| Invariant | never more than one router dialled, in any run |
+
+On the last row, precisely: the AC *did* report two `simdsl` sessions during the
+`session-control=disable` run — one live, one orphaned from the router that had
+just been destroyed, which that policy does not clean up. Only one live router
+was ever dialled. The count is a proxy for the real invariant and only a valid
+one while the AC enforces single-session, so it is reported as a `WARN` rather
+than silenced: an orphaned session still occupies the single slot at a real ISP,
+and that is exactly what made `deny` take 141–148s.
+
+## Two failure modes found by running it, not by reading it
+
+**The flap damper tore down a healthy WAN.** `ppp_dial()` checked the hold-off
+and returned *before* renewing `may-dial`. That file is a lease the guard
+expires after `LEASE_TTL`, so tripping the damper stopped the renewal and the
+guard hung up `pppoe0` **on the master** ~80s later:
+
+```
+DIAL FLAP: >=6 attempts in 600s -- holding off 900s
+GUARD: lease stale (81s > 75s) -- hanging up pppoe0
+```
+
+A damper meant to suppress repeated *dials* was destroying an established
+session instead. An active session now renews the lease and returns before
+every other check; everything below only decides whether to start a **new**
+session. T12 is the regression test.
+
+**A missing peers file is silent.** `/etc/ppp/peers/pppoe0` is both pppd's
+options file and the gate's second condition, and it is only written by a commit
+that touches the pppoe subtree. Without it systemd logs
+`skipped because of an unmet condition check` exactly once and then nothing —
+a router that cannot dial at all looks identical to a healthy backup.
+`ppp_dial()` now says so on every tick, and distinguishes the two causes:
+configured-but-not-rendered (re-commit the subtree) versus no `pppoe0` in the
+config at all.
+
+The second cause is the one to watch in production: **a commit that was never
+`save`d reverts on reboot and takes `pppoe0` with it.** That is exactly how the
+sim secondary lost its WAN and spent hours looking like an ISP problem. After
+any hand commit to the pppoe subtree, `save` — or the next reboot produces a
+standby that can never take over.
+
+## Deploying — steps 1–9 done 2026-09-06
+
+1. `sudo /config/vyos-known-good save` on both.
+2. `migration/vrrp-wan-install --vip 192.168.1.1 --host vyos@10.0.1.253` then the
+   same for `.252`. Then `--check` on both. **No config change yet** — verify
+   nothing dials.
+3. Confirm `/config/wan-secrets` is present and identical on both.
+4. **vyos002 first** (the non-master), on its own commit — `interfaces pppoe` is
+   priority 322 and one bad node fails everything:
+   `delete interfaces pppoe pppoe0 disable`, `commit-confirm 10`.
+5. Verify vyos002 did **not** dial — check on the wire, not from state:
+   `sudo tcpdump -i bond0.51 -nn pppoed` should show no PADI. Then `confirm`; `save`.
+6. vyos001: nothing to change; it already has `pppoe0` enabled.
+7. Confirm `vif 53 disable` is in **both** `config.boot`s. vyos001's lacked it;
+   fixed with `migration/vif53-pin-boot-disable` — see below.
+8. **Done 2026-09-06** (`kubernetes-deployment@45033dd`, on `main`). Both
+   overrides merged, transition-scripts applied to both boxes by hand rather
+   than left as drift, and `vyos:verify` is clean: 533 / 512 nodes, zero drift.
+   The staging file `migration/pulumi-override-pppoe-gated.json` is kept as the
+   record of why the ordering mattered. It was staged, unapplied, on purpose: another agent runs `pulumi up` on that repo, so
+   merging it *is* a production change made by someone else at a time you do not
+   choose. Removing `pppoe0 disable` from vyos002 before the gate exists there
+   lets it dial on the next commit and take the single Vodafone session off
+   vyos001. Run `npm run vyos:export && npm run vyos:render` first so the model
+   follows whichever router actually holds the WAN.
+9. Add the drop-in re-install to the VyOS image-upgrade runbook.
+   **Done** — `migration/VYOS-IMAGE-UPGRADE.md`. An upgrade replaces `/etc` and
+   so removes the gate; the reconciler fails closed, giving "PPPoE never
+   dials" rather than "both routers dial".
+
+Step 4 is the one that matters most and is worth stopping on. vyos002 has been
+in **FAULT on all six groups for over three days** — verified again while
+writing this, alongside vyos001 holding `192.168.1.1` on `bond0.1` and
+`pppoe0` up on `83.106.5.72`. Until vyos002 reaches BACKUP there is no standby
+at all: if vyos001 died today nothing would pick up the gateway VIPs. The
+existing `vrrp-health-check-wan-present` override predicted exactly this in its
+own reason text — *"with the primary genuinely dead the secondary stays FAULT
+and nothing holds the gateway. The fix for that is WAN-follows-master, which is
+a separate change."* This is that change.
+
+## Proven in production — controlled drill, 2026-09-06
+
+`migration/wan-drill` force-faulted vyos001 and timed a real failover:
+
+```
+TAKEOVER OK: vyos002 held the VIP and reached the internet in 52s
+FAILBACK OK: 36s
+```
+
+vyos002 took the VIPs at t+18s and had **both** WANs by t+52s. Failback put
+vyos001 back with a WAN in 36s. Total interruption ≈ 88s across two deliberate
+transitions.
+
+**The cloned-MAC lease transfers.** This was the largest untested item in the
+whole design — whether the 10 gig ISP would re-issue `87.192.101.48` to
+`f0:9f:c2:12:9b:4f` arriving on a different switch port. It did, same address,
+within the takeover window. That risk is now closed.
+
+**Vodafone did not refuse the re-dial**, so its `session-control` behaves like
+`replace` rather than the hostile `deny`. `GRACE=300` was sized against the
+sim's 148s `deny` case and is therefore comfortable — but it should stay where
+it is, because one drill on one evening does not establish the ISP's policy
+under all conditions.
+
+**Vodafone hands out a different IPv4 on every dial**: `83.106.5.72` →
+`90.251.153.180` (vyos002) → `90.251.142.103` (vyos001, after failback).
+Nothing may be pinned to the PPPoE address. The HE IPv6 tunnel is pinned to
+`87.192.101.48`, which is the **10 gig** (`bond0.53`) and stable across
+failover. Anything added later that hardcodes a WAN IP must use the 10 gig one,
+not `pppoe0`'s.
+
+> **CORRECTED 2026-09-06.** This paragraph originally continued "so `tun0`
+> survived untouched and IPv6 stayed up at 15.5ms." **That conclusion was
+> wrong, and it should never have been recorded as a result.** The premise is
+> right — the endpoint address is stable — but it does not follow. During
+> takeover the reconciler disables `bond0.53` on the demoted box, so
+> `87.192.101.48` *leaves vyos001 and appears on vyos002*, and vyos002 has no
+> `tun0` at all: no tunnel, no `he-tunnel-follow`, no `/config/he-secrets`, no
+> VLAN 9 prefix, no `route6 ::/0`. Inbound protocol 41 from HE lands on a router
+> with nothing to decapsulate it. vyos001's own journal for the drill window
+> reads `08:36:01 he-tunnel-follow: no default route; refusing to guess`.
+>
+> The reading was taken either side of the window, not through it — `wan-drill`
+> contained **no IPv6 check of any kind**, and neither did any other part of the
+> mechanism. That is now fixed: the drill probes IPv6 in both timing loops and
+> asserts that a router-level failover makes **zero** HE API calls. Until a
+> drill produces that figure, the IPv6 behaviour of a failover is *unmeasured*,
+> not "fine".
+>
+> The gap itself was real: **IPv6 was single-homed on vyos001 while the WAN
+> beneath it was HA.** **Closed and measured 2026-09-06** — see the drill below.
+
+Production takeover (52s) is about twice the sim's `replace` figure (26s), which
+is the expected direction: the VP2440s commit under kea, BGP and conntrack while
+the sim routers are idle.
+
+## IPv6 follows the WAN — measured, 2026-09-06
+
+The second drill of the day, run after IPv6-follows-master was deployed. This is
+the first time the IPv6 behaviour of a failover has been a **measurement** rather
+than an assertion:
+
+```
+TAKEOVER OK: vyos002 held the VIP and reached the internet in 37s
+IPv6 followed in 37s (v4 37s, gap 0s)
+FAILBACK OK in 32s
+IPv6 back in 44s
+tun0 src : 87.192.101.48 -> 87.192.101.48   OK: unchanged across the drill
+HE updates from vyos001: 0
+HE updates from vyos002: 0
+```
+
+Full log: `migration/drill-evidence/wan-drill-2026-09-06-ipv6.txt`.
+
+**Zero HE API calls across a full takeover and failback.** This is the invariant
+the design rests on and it now has evidence: the 10 gig lease follows the cloned
+MAC, so the tunnel endpoint is the *same address* on whichever router holds the
+WAN, and there is nothing to tell Hurricane Electric. Only the within-box fall
+back to PPPoE needs an HE update.
+
+**IPv6 is no longer the laggard, but the two directions are not symmetric.** On
+takeover it arrived in the same 5s sample as IPv4; on failback it trailed by 12s.
+That asymmetry is the reconciler's tick, not a fault: on promotion it enables
+`bond0.53` first, and `v6_take` only raises the tunnel once the source address
+actually exists, so it can land on the following 30s tick. Bound is one tick.
+Note the sampling granularity — the drill polls every 5s, so "gap 0s" means
+"within the same sample", not "simultaneous".
+
+Takeover was 37s here against 52s in the morning drill. Do not read that as an
+IPv6 improvement; it is the same IPv4 mechanism on a different run, and the
+morning figure included the first-ever cloned-MAC lease transfer.
+
+**Vodafone confirmed the every-dial-a-new-address behaviour again**: `pppoe0`
+came back as `90.251.152.236`, having been `90.251.142.103` before the drill.
+
+## config.boot pins `vif 53 disable` on both — fixed 2026-09-06
+
+The convention is that **both** `config.boot`s hold `vif 53 disable`, so a reboot
+in any order comes up unable to claim the cloned MAC and the reconciler enables
+it on whichever box holds the VIP. vyos001's did not; its `config.boot` predated
+this work.
+
+There is no clean way to express "boot disabled, run enabled" in VyOS: **`save`
+writes the RUNNING config, not the candidate.** Setting the node, saving and
+discarding was tested in labsim and `config.boot` came back *without* `disable`,
+the WAN untouched. So the node must genuinely be disabled, saved, and
+re-enabled. `migration/vif53-pin-boot-disable` does exactly that, is idempotent,
+and no-ops on a box that already has it.
+
+Cost, measured on vyos001: a **32s** window (10s in the sim — production commits
+under kea/BGP/conntrack are slower), `bond0.53` re-leased `87.192.101.48` 5s
+after re-enable, and `vyos-failover` restored the primary route about a minute
+later:
+
+```
+09:32:23  ip route del 0.0.0.0/0 ... dev bond0.53
+09:32:32  Check fail for route 0.0.0.0/0 interface "bond0.53"
+09:33:23  ip route add 0.0.0.0/0 via 87.192.96.1 dev bond0.53 metric 1 proto failover
+```
+
+The house rode `pppoe0` for that minute rather than losing the internet, which
+is the T5 path working. Note the shape of that recovery before reading a fresh
+`ip route show` as a regression: for ~60s after the bounce the default really is
+on `pppoe0`, because `vyos-failover` only re-adds the `bond0.53` route once its
+probes pass again.
+
+**A race worth knowing about.** The first sim run collided with
+`vrrp-wan-reconcile`'s own commit — *"Configuration system temporarily locked due
+to another commit in progress"* — and the `save` landed while the **re-enable did
+not**, leaving the master with its 10 gig down. The script now takes the
+reconciler's `/run/vrrp-wan.lock` (which the reconciler skips a tick rather than
+block on), with `9>&-` so the config session's unionfs child cannot inherit it.
+Even the bad run ended correctly — the reconciler logged *"MASTER with bond0.53
+disabled -> enabling"* and repaired it in 4s — so a half-completed run is
+survivable by design. The script no longer leans on that, and verifies the
+re-enable rather than reporting a success it did not achieve.
+
+**Rollback**, from either box: `set interfaces pppoe pppoe0 disable` on both and
+`rm /run/vrrp-wan/may-dial`. That restores today's behaviour exactly.
+
+## What the sim cannot prove
+
+- **Vodafone's `session-control`.** The matrix now brackets it properly.
+  Destroying the master and timing the survivor's session:
+
+  | policy | takeover |
+  |---|---|
+  | `replace` (accel-ppp default) | 26s / 26s |
+  | **`deny`** (hostile) | **148s / 141s** |
+  | `disable` | 21s / 20s |
+
+  `deny` is the sizing case: the AC refuses the survivor until its own
+  dead-peer timer frees the dead session, and the poller caught two dial
+  attempts being rejected before one succeeded. `GRACE` is set from that — see
+  `migration/vrrp-wan.conf`. This still cannot tell you which policy Vodafone
+  runs, and account rate-limiting or lockout on repeated dials has no sim
+  analogue at all; the flap damper (6 dials / 600s → 15 min hold-off) exists
+  for that.
+
+  Treat the 148s as a floor rather than a worst case. These are idle 2-vCPU
+  VMs, and the AC shares an OVS bridge with the routers, so `virsh destroy`
+  removes the port and accel-ppp sees the peer physically vanish. A real BRAS
+  reached over DSL does not learn that our router died — it waits out its own
+  timers, which are longer and not ours to know.
+
+  Worth knowing how close this came to being missed: until 2026-09-06 the
+  matrix set the policy with `vbash -c 'source script-template; configure;
+  ...; commit'`, which never starts a config session. `commit` failed to
+  stderr, the helper discarded it, and all three iterations ran against the
+  default while printing the mode they were supposedly testing. It reported
+  `deny` at 25s. The real figure is 148s.
+- **Whether Vodafone honours our LCP Terminate / PADT** on a graceful stop.
+- ~~**The cloned-MAC lease.**~~ **Answered 2026-09-06**: the drill moved it and
+  the ISP re-issued `87.192.101.48` to `f0:9f:c2:12:9b:4f` on vyos002's port
+  within the takeover window. See "Proven in production" above.
+- ~~**Whether VyOS can dial Vodafone at all.**~~ **Answered 2026-09-06**: both
+  routers dialled successfully during the drill. MTU/MSS under sustained load
+  is still unmeasured, and Vodafone hands out a different IPv4 every dial.
+- **Timing under load.** The sim routers are idle 2-vCPU VMs; commit latency on
+  the VP2440s under kea + BGP + conntrack will be worse, and commit latency is
+  the dominant term in the `bond0.53` half of a failover.
+
+## How the model handles the asymmetry — resolved
+
+An earlier draft of this file said an override "must assert `vif 53 disable` on
+**both** routers". **That advice was wrong and has been removed**; do not
+reintroduce it. `vif 53 disable` is *runtime* state owned by
+`vrrp-wan-reconcile`, keyed on who holds the management VIP, so pinning it in
+the model would fight the reconciler on every apply and would briefly disable
+the live master's 10 gig each time.
+
+What is actually done, and why it is safe:
+
+- **Runtime (Pulumi): follow reality.** Run `npm run vyos:export && npm run
+  vyos:render` immediately before any `pulumi up` touching vyos. Whichever
+  router currently holds the WAN keeps it; the apply is a no-op on that node.
+  There is deliberately **no** override for `vif 53 disable`.
+- **Boot (`config.boot`): hardcode safe.** Both routers pin `vif 53 disable`,
+  so a reboot in any order comes up unable to claim the cloned MAC and the
+  reconciler enables it on whoever holds the VIP. See the section above.
+- **Install time (PXE, nothing to follow).** `migration/vyos-mode-delta.py`
+  emits `vif 53 disable` for a box with no WAN, and deliberately does *not*
+  emit `pppoe pppoe0 disable`.
+
+Verified 2026-09-06: `vyos:verify` reports both routers in sync, 533 and 512
+nodes, zero drift.

migration/RECOVERY-CARD-vlan1-move.md

@@ -0,0 +1,194 @@
+# Recovery card — moving Management to tagged VLAN 1
+
+Print or keep open. **During this change there is no internet, so no Claude.**
+Everything you need is on this page.
+
+---
+
+## The one thing that matters
+
+```
+ssh vyos@10.0.1.252
+```
+
+Your workstation is `10.0.0.210/23`; vyos001's LoT leg is `10.0.1.252/23`. Same
+subnet, same VLAN, **direct L2** — verified: `ip route get` returns
+`dev lanbr0 src 10.0.0.210` with no `via`, MAC `64:62:66:25:96:45`.
+
+It therefore does **not** depend on: the Management VLAN, VRRP, the VIPs,
+inter-VLAN routing, DNS, or the switch trunk config. If the router is up and its
+bond has link, this works. `bond0.10` is untouched by the change and stays in the
+firewall `LAN` group throughout.
+
+vyos002, once it is up, is `10.0.1.253` the same way.
+
+Other legs that also survive: `192.168.3.4` (kvm), `192.168.2.252` (Roomates).
+
+---
+
+## Before you touch anything
+
+```
+ssh vyos@10.0.1.252
+sudo /config/vyos-known-good save
+```
+
+The existing snapshot is from **2026-08-24** and predates today's fixes
+(eth2 removal, VRRP health-check) — restoring that one would undo them. Take a
+fresh one first. Check with `sudo /config/vyos-known-good status`.
+
+---
+
+## Order: switch FIRST, router SECOND
+
+This matters and is easy to get backwards.
+
+The UniFi controller is `192.168.1.5`, on the **Management** VLAN. Your
+workstation is on LoT and reaches it *through vyos001*. The moment the router
+has Management on `bond0.1` while the switch is still sending it untagged, that
+routing is dead — **and you lose the controller**, which is the thing you still
+need in order to change the switch.
+
+So:
+
+1. **UniFi first**, while everything still works:
+   USW Aggregation → port 1 `firewall001` (LAG, members 1+2) →
+   Native VLAN: Management → **None**, and make sure VLAN 1 is tagged/allowed.
+   *vyos001 loses Management the instant this lands. That is expected.*
+   Do **not** touch port 3 `firewall002` — that is vyos002, and it is down.
+2. **Router second**, over `ssh vyos@10.0.1.252` (still works — L2 direct).
+
+If UniFi will not offer "no native VLAN", stop and read *"If UniFi cannot do it"*
+below rather than improvising.
+
+---
+
+## The router change
+
+```
+ssh vyos@10.0.1.252
+configure
+set interfaces bonding bond0 vif 1 address '192.168.1.252/24'
+set interfaces bonding bond0 vif 1 description 'management'
+delete interfaces bonding bond0 address
+set firewall group interface-group LAN interface 'bond0.1'
+delete firewall group interface-group LAN interface 'bond0'
+set high-availability vrrp group native interface 'bond0.1'
+commit-confirm 10
+save
+exit
+```
+
+**Use `commit-confirm 10`, not `commit`.** If it goes wrong and you cannot get
+back in, the router reverts itself after 10 minutes and comes back on its own.
+That is your safety net with no internet and no help.
+
+Once you have confirmed it works (below), run:
+
+```
+configure
+confirm
+save
+exit
+```
+
+`save` after `confirm`, or a reboot loses it.
+
+### Then, and this is the step that gets forgotten
+
+```
+sudo systemctl restart isc-kea-dhcp4-server
+```
+
+VyOS does **not** restart kea for an interface address change. Without this it
+keeps a raw socket bound to the old address and keeps handing out wrong-VLAN
+addresses — the fix looks like it did nothing. Give it ~60s before judging;
+kea reopens sockets on a retry loop and answers nothing for a while after a
+restart (measured: still silent at 55s in the sim, then fine).
+
+Also check DNS came back, since the forwarder binds the VIP `192.168.1.1`:
+
+```
+sudo systemctl status pdns-recursor --no-pager | head -3
+dig @192.168.1.1 google.com +short
+```
+
+---
+
+## Verify
+
+```
+ssh vyos@192.168.1.252          # Management back, now tagged
+show vrrp                        # native should be on bond0.1
+show dhcp server leases | head
+```
+
+Then from a machine on VLAN 3, force a DHCP renew and confirm it gets a
+`192.168.3.x` address and not a `192.168.1.x` one.
+
+---
+
+## If you are locked out
+
+In order:
+
+1. **Wait 10 minutes.** `commit-confirm` reverts by itself. This is the answer
+   most of the time. Do not power-cycle during this — you will lose the revert.
+2. `ssh vyos@10.0.1.252` — the LoT leg. Then `configure` / `rollback 1` / `commit`.
+3. Other legs: `ssh vyos@192.168.3.4`, `ssh vyos@192.168.2.252`.
+4. `sudo /config/vyos-known-good restore` — back to the snapshot you took at the
+   start. It is itself commit-confirmed, so even this cannot strand you.
+5. Put the UniFi port back: Native VLAN → Management on USW Aggregation port 1.
+   That alone restores the old shape and Management comes back untagged.
+
+**Do not** power-cycle vyos001 as a first move. Everything above is faster and
+non-destructive, and a reboot loses an unsaved `commit-confirm` revert.
+
+---
+
+## Do NOT power on vyos002 yet
+
+It still has `interfaces ethernet eth2 address 192.168.8.144/23` on the box — the
+same subnet as `bond0.2`. That is what ARP-poisoned `192.168.8.1` and took the
+cluster down. It also has no `/config/vrrp-wan-health`, so it can take the
+floating IPs with no WAN.
+
+Its console (`kvm - vyos002`, US24 port 9) is currently **unreachable** — it sits
+on a VLAN 3 port holding a Management lease `192.168.1.28`, which is the very bug
+being fixed here. Fixing DHCP first is what gets that console back.
+
+---
+
+## If UniFi cannot do it
+
+Classic UniFi (this is a classic controller, 10.4.57) may not offer
+"Native VLAN = None" — every switch port has a PVID. Two things make this awkward
+here: Management is UniFi's *default* network with **no VLAN ID at all**
+(`vlan: null`), so there may be nothing to "tag VLAN 1" with.
+
+If so, **stop and change nothing.** The workaround is to point the trunk's native
+VLAN at a VLAN the router does not serve (so `bond0` still ends up with no
+subnet), which needs a throwaway VLAN-only network created first. That is a
+design decision, not something to improvise at 1am with no internet. Put the port
+back to Native = Management and everything returns to today's working state.
+
+---
+
+## Facts worth having on paper
+
+| | |
+|---|---|
+| vyos001 Management | `192.168.1.252` → becomes `bond0.1` |
+| vyos001 LoT (recovery) | `10.0.1.252`, L2-direct from your workstation |
+| vyos002 Management | `192.168.1.253` (down) |
+| VIP Management | `192.168.1.1` |
+| UniFi controller | `192.168.1.5` (on Management — you lose it mid-change) |
+| firewall001 trunk | USW Aggregation port 1, LAG members 1+2 |
+| firewall002 trunk | USW Aggregation port 3, LAG members 3+4 |
+| SSH user / pass | `vyos` / `vyos` |
+| vyos001 bond MAC | `64:62:66:25:96:45` |
+
+Measured in labsim: converting the router while the peer is already converted
+costs **0s** of VIP downtime; converting it while it holds the VIPs costs about
+**6s**. vyos002 is down, so vyos001 holds everything — expect the ~6s, and expect
+Management to be gone from the UniFi change until the router change lands.

migration/RECOVERY-CARD-wan-panic.md

@@ -0,0 +1,99 @@
+# RECOVERY CARD — internet is down after a WAN failover
+
+No internet means no Claude. Everything here runs from the routers themselves.
+**Print this or keep it on a phone.**
+
+## 1. Get to a router
+
+The LoT leg is L2-direct on `bond0.10`. It survives Management, VRRP and
+routing being broken:
+
+```
+ssh vyos@10.0.1.252     # vyos001  (normally MASTER, has the WAN)
+ssh vyos@10.0.1.253     # vyos002  (normally BACKUP, has nothing)
+```
+
+Password is the usual one. If SSH is dead, use the JetKVM consoles.
+
+## 2. See what is going on
+
+```
+sudo /config/wan-panic status
+```
+
+Run it on both. You want exactly ONE box saying `holds VIP : YES`, and that
+same box showing a `WAN` line and a `route`.
+
+| what you see | what it means |
+|---|---|
+| one box `YES` with WAN + route | healthy, look elsewhere for the fault |
+| one box `YES`, **no WAN**, no route | the failover half-worked — go to §3 |
+| **both** `YES` | VRRP split — go to §3, run it on vyos002 |
+| **neither** `YES` | both faulted — go to §4 |
+
+## 3. Give the WAN back to vyos001
+
+**Run this on vyos002 (`10.0.1.253`).** This is the one that matters — vyos002
+standing down is what lets vyos001 take over.
+
+```
+sudo /config/wan-panic
+```
+
+Wait ~30s. Then on vyos001 (`10.0.1.252`):
+
+```
+sudo /config/wan-panic status
+```
+
+Expect `holds VIP : YES` and a `WAN` line with `bond0.53=…` and/or `pppoe0=…`.
+
+Once the house is back online and you want vyos002 to be a standby again:
+
+```
+sudo rm /run/vrrp-wan/force-fault        # on vyos002
+```
+
+Leave it set if you would rather have no standby than any more surprises —
+that is the pre-2026-09-06 arrangement and the house runs fine on it.
+
+## 4. Stop the mechanism touching anything
+
+If the WAN keeps moving, or you do not trust the automation:
+
+```
+sudo /config/wan-panic undo              # on BOTH routers
+```
+
+Stops the reconcile and guard timers. Whatever WAN is up **stays** up. Nothing
+will move it again until you re-enable the timers:
+
+```
+sudo systemctl enable --now vrrp-wan-reconcile.timer vrrp-wan-guard.timer
+```
+
+## 5. Nuclear — put the config back
+
+Only if the config itself is wrong. **This reboots the router.**
+
+```
+sudo /config/vyos-known-good restore     # on BOTH routers
+```
+
+The pinned config is from 2026-09-06, immediately before the PPPoE HA rollout:
+1112 lines on vyos001, 1069 on vyos002.
+
+## Why the WAN can only be on one box
+
+One ISP account each way. The 10 gig lease is bound to a cloned MAC
+(`f0:9f:c2:12:9b:4f`, the old USG's) and Vodafone is a single-session PPPoE
+credential. Two routers holding either at once is worse than one holding
+neither — that is why the safe state is "vyos001 has it, vyos002 is inert".
+
+## Known gap
+
+vyos001's `config.boot` does not carry `vif 53 disable`. If vyos001 reboots
+**while vyos002 is master**, the cloned MAC is briefly live on both. It clears
+itself within 30s (the reconciler disables it on the non-master). If you see
+MAC flapping on the WAN switch port right after a vyos001 reboot, that is this,
+and it will stop on its own.

migration/VYOS-IMAGE-UPGRADE.md

@@ -0,0 +1,92 @@
+# Upgrading a VyOS image on the router pair
+
+VyOS keeps `/config` across an image upgrade and **replaces `/etc`**. Everything
+in `/config` survives; anything the WAN mechanism put in `/etc` does not.
+
+## What an upgrade silently removes
+
+`/etc/systemd/system/ppp@pppoe0.service.d/10-vrrp-wan-gate.conf` — the gate.
+
+That drop-in is the only thing stopping the **backup** from dialling. With
+`pppoe0` enabled on both routers (which it is, by design), `interfaces_pppoe.py`
+restarts ppp on every commit touching the pppoe subtree when the daemon is not
+running. Without the gate, the backup dials on the next `pulumi up`, hand
+commit, or boot-time config load — and Vodafone is a single-session account, so
+it takes the session off the live master.
+
+`vrrp-wan-reconcile` fails **closed** here: it refuses to dial at all when the
+drop-in is missing, and logs
+
+```
+REFUSING to dial: gate drop-in ... is missing (VyOS upgrade?)
+```
+
+so the symptom is "PPPoE never comes up", not "both routers dialled". That is
+the safe direction, but it does mean an upgraded router has no PPPoE until the
+gate is reinstalled.
+
+The systemd **units and timers** also live in `/etc` and go the same way.
+
+## Do this, one router at a time
+
+Never both at once — the surviving router must be able to hold the VIPs.
+
+1. **Upgrade the BACKUP first.** Confirm which it is:
+   ```
+   sudo /config/wan-panic status          # "holds VIP : no"
+   ```
+2. Install the image and reboot as normal.
+3. **Reinstall the mechanism** from a checkout of `lab`:
+   ```
+   migration/vrrp-wan-install --vip 192.168.1.1 --host vyos@<router>
+   migration/vrrp-wan-install --check  --host vyos@<router>     # must be clean
+   ```
+4. **Verify the gate is shut and nothing dialled:**
+   ```
+   systemctl show ppp@pppoe0 -p ConditionResult -p ActiveState -p NRestarts
+   ```
+   Want `ConditionResult=no`, `ActiveState=inactive`, `NRestarts=0`. Check the
+   wire too, not just state: `sudo tcpdump -i bond0.51 -nn pppoed` — no PADI.
+5. Confirm it reaches **BACKUP**, not FAULT:
+   ```
+   show vrrp
+   ```
+   FAULT on every group means the health check is failing — most likely
+   `/config/vrrp-wan-health` did not get reinstalled, or `vrrp-wan.conf` is
+   missing so `GRACE` and the VIP fall back to defaults.
+5b. **Check IPv6 came back with it.** `vrrp-wan-install` now carries
+   `he-tunnel-follow`, so `--check` covers it, but `/config/he-secrets` is a
+   secret placed by Pulumi and is only checked for *presence*:
+   ```
+   sudo /config/he-tunnel-follow status      # role, tunnel src, MTU
+   ```
+   Want the box's own role, and — on the master — a tunnel source equal to the
+   **10 gig** address with MTU 1480. `/config` survives an upgrade, so the
+   `system task-scheduler` entry that runs this every minute survives too; it is
+   the units and the ppp gate in `/etc` that do not.
+6. Confirm `config.boot` still pins the safe resting state:
+   ```
+   sudo /config/vif53-pin-boot-disable --check    # config.boot disable : 1
+   ```
+7. Only once the upgraded box is a healthy BACKUP, fail over and repeat for the
+   other router. `migration/wan-drill` does that unattended, or by hand:
+   `sudo /config/wan-panic` on the box you want to give up mastership.
+
+## After both are done
+
+```
+migration/vrrp-wan-install --check --host vyos@10.0.1.252
+migration/vrrp-wan-install --check --host vyos@10.0.1.253
+cd kubernetes-deployment && npm run vyos:export -- --router vyos001=10.0.1.252 --router vyos002=10.0.1.253
+npm run vyos:render && npm run vyos:verify -- --router vyos001=10.0.1.252 --router vyos002=10.0.1.253
+```
+
+Both should read "in sync". If the export shows `interfaces pppoe pppoe0
+disable` coming back, something reinstated it — the
+`pppoe-gated-not-config-disabled` override exists to prevent exactly that, so
+check it is still in `infra/vyos/subtrees/overrides.json`.
+
+## If it goes wrong
+
+`migration/RECOVERY-CARD-wan-panic.md`, or `/config/RECOVERY-CARD.md` on either
+router. Short version, on vyos002: `sudo /config/wan-panic`.

migration/_unifi.py

@@ -0,0 +1,84 @@
+"""Shared UniFi API client for the migration tooling.
+
+The controller is a CLASSIC self-hosted UniFi Network app (server_version
+10.4.x), not UniFi OS: login is /api/login and data lives under
+/api/s/<site>/... . UniFi OS would use /api/auth/login + /proxy/network/api.
+Credentials come from the mcpctl server definition so they are not duplicated
+here.
+"""
+from __future__ import annotations
+
+import json, re, ssl, subprocess, urllib.request, http.cookiejar
+
+
+def client():
+    raw = subprocess.run(["mcpctl", "describe", "server", "unifi-network"],
+                         capture_output=True, text=True).stdout
+    m = re.search(r"UNIFI_TARGETS\s+(\[.*)", raw)
+    if not m:
+        raise SystemExit("could not read UNIFI_TARGETS from mcpctl")
+    blob = m.group(1).strip()
+    try:
+        targets = json.loads(blob)
+    except json.JSONDecodeError:
+        targets = json.loads(blob + "}" * (blob.count("{") - blob.count("}")))
+    t = targets[0]
+    base = t["base_url"].rstrip("/")
+    auth = t.get("auth", {})
+    site = t.get("default_site", "default")
+
+    ctx = ssl.create_default_context()
+    ctx.check_hostname = False
+    ctx.verify_mode = ssl.CERT_NONE
+    opener = urllib.request.build_opener(
+        urllib.request.HTTPCookieProcessor(http.cookiejar.CookieJar()),
+        urllib.request.HTTPSHandler(context=ctx))
+    req = urllib.request.Request(
+        f"{base}/api/login",
+        data=json.dumps({"username": auth.get("username"),
+                         "password": auth.get("password")}).encode(),
+        headers={"Content-Type": "application/json"})
+    opener.open(req, timeout=20).read()
+    return opener, base, site
+
+
+def get(opener, base, site, path):
+    """GET /api/s/<site>/<path>, returning the `data` list (never raising)."""
+    try:
+        body = opener.open(f"{base}/api/s/{site}/{path}", timeout=30).read()
+        return json.loads(body).get("data", [])
+    except Exception as exc:
+        return {"__error__": f"{type(exc).__name__}: {exc}"}
+
+
+def post(opener, base, site, path, payload):
+    """POST to /api/s/<site>/<path> -- used for device commands (cmd/devmgr)."""
+    req = urllib.request.Request(
+        f"{base}/api/s/{site}/{path}",
+        data=json.dumps(payload).encode(),
+        headers={"Content-Type": "application/json"}, method="POST")
+    try:
+        return json.loads(opener.open(req, timeout=30).read()).get("data", [])
+    except urllib.error.HTTPError as exc:
+        return {"__error__": f"HTTP {exc.code}: {exc.read()[:300].decode(errors='replace')}"}
+    except Exception as exc:
+        return {"__error__": f"{type(exc).__name__}: {exc}"}
+
+
+def put(opener, base, site, path, payload):
+    """PUT to /api/s/<site>/<path>. Returns the `data` list or an __error__ dict.
+
+    Classic controllers accept the session cookie alone -- no CSRF token, which
+    UniFi OS would require. Errors are returned rather than raised so a caller
+    changing production config can report and stop rather than traceback.
+    """
+    req = urllib.request.Request(
+        f"{base}/api/s/{site}/{path}",
+        data=json.dumps(payload).encode(),
+        headers={"Content-Type": "application/json"}, method="PUT")
+    try:
+        return json.loads(opener.open(req, timeout=30).read()).get("data", [])
+    except urllib.error.HTTPError as exc:
+        return {"__error__": f"HTTP {exc.code}: {exc.read()[:300].decode(errors='replace')}"}
+    except Exception as exc:
+        return {"__error__": f"{type(exc).__name__}: {exc}"}

migration/drill-evidence/wan-drill-2026-09-06-ipv6.txt

@@ -0,0 +1,38 @@
+LOG=/tmp/claude-1000/-home-michal-developer-michalzxc-claude-lab/d66e2cbb-c178-46d7-a628-0ecb17b48a09/scratchpad/wan-drill-150954.log
+15:09:54 === pre-flight ===
+15:09:54 holder now   : 10.0.1.252
+15:09:54 10.0.1.252 WAN      : bond0.53=87.192.101.48 pppoe0=90.251.142.103 
+15:09:55 10.0.1.253 WAN      : 
+15:09:55 internet     : UP via 10.0.1.252
+15:09:56 10.0.1.252 tun0 src : 87.192.101.48
+15:09:56 10.0.1.253 tun0 src : 87.192.101.48
+15:09:56 IPv6         : UP via 10.0.1.252
+15:09:56 === arming auto-abort on 10.0.1.253 ===
+  watchdog armed (pid 1014868): stand down after 150s holding the VIP with no WAN
+15:09:56 === DRILL: force-faulting 10.0.1.252 ===
+15:10:03   t+7s holder=10.0.1.252  vyos002_wan=[]  v6=down
+15:10:09   t+13s holder=10.0.1.252  vyos002_wan=[]  v6=down
+15:10:15   t+19s holder=10.0.1.253  vyos002_wan=[]  v6=down
+15:10:21   t+25s holder=10.0.1.253  vyos002_wan=[]  v6=down
+15:10:33   t+37s holder=10.0.1.253  vyos002_wan=[bond0.53=87.192.101.48 ]  v6=up
+15:10:33 *** TAKEOVER OK: 10.0.1.253 held the VIP and reached the internet in 37s ***
+15:10:33 *** IPv6 followed in 37s (v4 37s, gap 0s) ***
+15:10:33 === failing back to 10.0.1.252 ===
+15:10:46   t+13s holder=10.0.1.253  vyos001_wan=[]  v6=down
+15:10:53   t+20s holder=10.0.1.253  vyos001_wan=[]  v6=down
+15:10:59   t+26s holder=10.0.1.252  vyos001_wan=[]  v6=down
+15:11:04   t+31s holder=10.0.1.252  vyos001_wan=[bond0.53=87.192.101.48 ]  v6=down
+15:11:11   t+38s holder=10.0.1.252  vyos001_wan=[bond0.53=87.192.101.48 ]  v6=down
+15:11:17   t+44s holder=10.0.1.252  vyos001_wan=[bond0.53=87.192.101.48 ]  v6=up
+15:11:17 *** FAILBACK OK in 32s ***
+15:11:17 *** IPv6 back in 44s ***
+15:11:17 === IPv6 invariants ===
+15:11:17 tun0 src     : 87.192.101.48 -> 87.192.101.48
+15:11:17   OK: tunnel source unchanged across the drill
+15:11:18 HE updates from 10.0.1.252 since 2026-09-06 15:09:54: 0
+15:11:18 HE updates from 10.0.1.253 since 2026-09-06 15:09:54: 0
+15:11:18 --- cleanup (always runs) ---
+15:11:39 final holder : 10.0.1.252
+15:11:40 final WAN    : 10.0.1.252 [bond0.53=87.192.101.48 pppoe0=90.251.152.236 ]  10.0.1.253 []
+15:11:40 final internet: UP via 10.0.1.252
+15:11:40 log: /tmp/claude-1000/-home-michal-developer-michalzxc-claude-lab/d66e2cbb-c178-46d7-a628-0ecb17b48a09/scratchpad/wan-drill-150954.log

migration/he-tunnel-follow

@@ -0,0 +1,181 @@
+#!/bin/bash
+# Keep the Hurricane Electric 6in4 tunnel pointed at whichever WAN is live.
+#
+# The tunnel is anchored to a source IPv4. When failover moves the default route
+# from the 10 gig to PPPoE, 6in4 packets keep leaving with the old source, HE
+# drops them, and IPv6 goes dark while IPv4 keeps working -- a partial outage
+# that presents as "some sites are broken", which is far worse to diagnose than
+# a clean one.
+#
+# Installed on BOTH routers and gated on VRRP mastership: the backup exits
+# immediately, and vrrp-wan-reconcile brings tun0 up and calls this script the
+# moment it takes the VIP. The HE endpoint itself needs no update when the WAN
+# moves between routers -- 87.192.101.48 is the 10 gig lease bound to the cloned
+# MAC, so it follows the VIP to the other box unchanged (proven by the 2026-09-06
+# drill). HE only has to be told about the WITHIN-box fall back to PPPoE.
+#
+# Changes are made at KERNEL level (`ip tunnel change`), not in VyOS config, on
+# purpose:
+#   - no commit per WAN flip, so a flapping line cannot churn the config;
+#   - no drift against the Pulumi model, so `vyos-verify` stays meaningful;
+#   - a reboot restores config.boot, which pins the 10 gig -- the correct
+#     default -- so the wrong state cannot survive a restart.
+#
+#   he-tunnel-follow status     what is live vs what should be (read-only)
+#   he-tunnel-follow run        reconcile, updating HE if the source changed
+#   he-tunnel-follow run --dry  say what it would do, change nothing
+#
+# Credentials in /config/he-secrets (0600), NOT in git:
+#   HE_USER=<tunnelbroker username>
+#   HE_UPDATE_KEY=<from the tunnel's Advanced tab -- replaces the account password>
+#   HE_TUNNEL_ID=<numeric tunnel id>
+set -uo pipefail
+
+TUNNEL="${TUNNEL:-tun0}"
+SECRETS="${SECRETS:-/config/he-secrets}"
+STATE="${STATE:-/run/he-tunnel-follow.state}"
+ROLE_STATE="${ROLE_STATE:-/run/he-tunnel-follow.role}"
+
+# HE's update endpoint, as a variable so labsim can point it at a stub. The sim
+# has no public IPv4 and no HE account, which is the whole reason the tunnel was
+# never rehearsed; with this the sim can exercise the HE-side half too.
+HE_UPDATE_URL="${HE_UPDATE_URL:-https://ipv4.tunnelbroker.net/nic/update}"
+
+# This script is installed on BOTH routers -- the same principle as the PPPoE
+# gate: configured identically everywhere, gated at runtime. So it must know
+# when it is the backup. Left ungated, the backup copy either dies on "no
+# default route" every minute, or, far worse, sees its own idle pppoe0 address
+# and points the HE endpoint at it. Vodafone hands out a different IPv4 on every
+# dial, so that is an IPv6 blackhole plus a wasted write against a rate-limited
+# API -- and it would fire on the backup, where nobody is looking.
+#
+# The VIP comes from the same /config/vrrp-wan.conf the reconciler and the
+# health check read, so there is exactly one definition of "master" on the box.
+WAN_CONF="${WAN_CONF:-/config/vrrp-wan.conf}"
+# shellcheck disable=SC1090
+[ -r "$WAN_CONF" ] && . "$WAN_CONF"
+VIP="${VRRP_WAN_VIP:-192.168.1.1}"
+# 6in4 costs 20 bytes. The 10 gig path is 1500 -> 1480; PPPoE is 1492 -> 1472.
+# Getting this wrong is the classic "IPv6 works until something large" failure.
+declare -A WAN_MTU=( ["bond0.53"]=1480 ["pppoe0"]=1472 )
+# Require the same answer twice before acting. HE rate-limits updates, and a
+# flapping WAN would otherwise hammer the API exactly when it is needed most.
+HYSTERESIS="${HYSTERESIS:-2}"
+
+log() { logger -t he-tunnel-follow -- "$*"; printf '  %s\n' "$*"; }
+die() { logger -t he-tunnel-follow -p user.err -- "$*"; printf '  ERROR: %s\n' "$*" >&2; exit 1; }
+
+holds_vip()  { ip -4 -o addr show 2>/dev/null | grep -q " ${VIP}/"; }
+active_wan() { ip -4 route show default 2>/dev/null | awk '/^default/{for(i=1;i<=NF;i++) if($i=="dev") print $(i+1); exit}'; }
+addr_of()    { ip -4 -br addr show "$1" 2>/dev/null | awk '{print $3}' | cut -d/ -f1; }
+tunnel_src() { ip tunnel show "$TUNNEL" 2>/dev/null | sed -nE 's/.* local ([0-9.]+).*/\1/p'; }
+tunnel_mtu() { cat "/sys/class/net/$TUNNEL/mtu" 2>/dev/null; }
+
+# HE's dyndns-style endpoint. `myip` is passed EXPLICITLY rather than letting HE
+# infer it from the request source: mid-failover the request itself may egress
+# either line, and inferring would happily point the tunnel at the WAN we just
+# left.
+he_update() {
+  local ip="$1"
+  [ -r "$SECRETS" ] || die "no $SECRETS -- create it with HE_USER / HE_UPDATE_KEY / HE_TUNNEL_ID (0600)"
+  # shellcheck disable=SC1090
+  . "$SECRETS"
+  [ -n "${HE_USER:-}" ] && [ -n "${HE_UPDATE_KEY:-}" ] && [ -n "${HE_TUNNEL_ID:-}" ] \
+    || die "$SECRETS is missing HE_USER, HE_UPDATE_KEY or HE_TUNNEL_ID"
+
+  local out
+  out="$(curl -sS --max-time 25 \
+      --data-urlencode "username=$HE_USER" \
+      --data-urlencode "password=$HE_UPDATE_KEY" \
+      --data-urlencode "hostname=$HE_TUNNEL_ID" \
+      --data-urlencode "myip=$ip" \
+      "$HE_UPDATE_URL" 2>&1)"
+  # dyndns protocol: "good <ip>" or "nochg <ip>" are both success.
+  case "$out" in
+    good*|nochg*) log "HE endpoint set to $ip ($out)"; return 0 ;;
+    *)            die "HE update refused: $out" ;;
+  esac
+}
+
+# Log only when the role CHANGES. On a 1-minute timer an unconditional line
+# would be 1440 entries a day on the backup, which is how a real message gets
+# lost. The marker lives in /run, so a reboot re-announces the role once.
+note_role() {
+  local role="$1" last=""
+  [ -r "$ROLE_STATE" ] && read -r last < "$ROLE_STATE"
+  [ "$last" = "$role" ] && return 0
+  echo "$role" > "$ROLE_STATE"
+  log "role is now $role"
+}
+
+reconcile() {
+  local dry="${1:-}"
+  local wan src want_mtu cur_src cur_mtu
+
+  # The backup owns nothing here. vrrp-wan-reconcile holds tun0 down on this box
+  # and will run this script itself the moment it takes the VIP, so there is
+  # nothing to do and nothing to say.
+  if ! holds_vip; then
+    note_role backup
+    rm -f "$STATE"          # start a promoted box with a clean hysteresis count
+    return 0
+  fi
+  note_role master
+
+  wan="$(active_wan)"; [ -n "$wan" ] || die "no default route; refusing to guess"
+  src="$(addr_of "$wan")"; [ -n "$src" ] || die "no IPv4 address on $wan"
+  want_mtu="${WAN_MTU[$wan]:-}"
+  [ -n "$want_mtu" ] || die "unknown WAN '$wan' -- add it to WAN_MTU rather than guessing an MTU"
+  cur_src="$(tunnel_src)"; cur_mtu="$(tunnel_mtu)"
+
+  if [ "$cur_src" = "$src" ] && [ "$cur_mtu" = "$want_mtu" ]; then
+    rm -f "$STATE"
+    log "in sync: $TUNNEL via $wan src $src mtu $cur_mtu"
+    return 0
+  fi
+
+  # Hysteresis: count consecutive runs agreeing on the same target.
+  local seen=0 last=""
+  [ -r "$STATE" ] && { read -r last seen < "$STATE"; }
+  if [ "$last" = "$src" ]; then seen=$((seen + 1)); else seen=1; fi
+  echo "$src $seen" > "$STATE"
+  if [ "$seen" -lt "$HYSTERESIS" ]; then
+    log "change seen ($cur_src -> $src) but waiting for stability ($seen/$HYSTERESIS)"
+    return 0
+  fi
+
+  if [ "$dry" = "--dry" ]; then
+    log "DRY RUN: would set HE endpoint to $src, then $TUNNEL local $src mtu $want_mtu"
+    return 0
+  fi
+
+  # HE first, then local. Either order costs a brief drop, but changing locally
+  # first guarantees HE discards our packets for the whole window.
+  he_update "$src" || return 1
+  sudo ip tunnel change "$TUNNEL" mode sit local "$src" || die "failed to set tunnel local address"
+  sudo ip link set "$TUNNEL" mtu "$want_mtu"            || die "failed to set tunnel MTU"
+  rm -f "$STATE"
+  log "moved $TUNNEL to $wan: src $cur_src -> $src, mtu $cur_mtu -> $want_mtu"
+}
+
+case "${1:-status}" in
+  status)
+    wan="$(active_wan)"
+    printf '  role       : %s (vip %s)\n' "$(holds_vip && echo master || echo backup)" "$VIP"
+    printf '  active WAN : %s\n' "${wan:-<none>}"
+    printf '  wan addr   : %s\n' "$(addr_of "${wan:-lo}")"
+    printf '  tunnel     : %s\n' "$(ip -br link show "$TUNNEL" 2>/dev/null | awk '{print $2}' || echo '<absent>')"
+    printf '  tunnel src : %s\n' "$(tunnel_src)"
+    # `${WAN_MTU[$wan]}` with an EMPTY subscript is a hard bash error --
+    # "bad array subscript" -- not an empty expansion, and the :- default never
+    # gets a chance to apply. A backup router has no default route, so `wan` is
+    # empty there and `status` printed an error line on exactly the box whose
+    # state you most need to read. Only index the array once there is a key.
+    printf '  tunnel mtu : %s (want %s)\n' "$(tunnel_mtu)" \
+        "$([ -n "${wan:-}" ] && echo "${WAN_MTU[$wan]:-?}" || echo '- (no WAN; this box is not master)')"
+    printf '  he endpoint: %s\n' "$HE_UPDATE_URL"
+    [ -r "$SECRETS" ] && printf '  credentials: present\n' || printf '  credentials: MISSING (%s)\n' "$SECRETS"
+    ;;
+  run) reconcile "${2:-}" ;;
+  *)   die "usage: he-tunnel-follow {status|run [--dry]}" ;;
+esac

migration/ppp-vrrp-gate.conf

@@ -0,0 +1,50 @@
+# Installed to /etc/systemd/system/ppp@pppoe0.service.d/10-vrrp-wan-gate.conf
+#
+# This drop-in is the ONLY thing preventing both routers from dialling the one
+# ISP credential at the same time. Do not remove it without reading this.
+#
+# pppoe0 is configured identically and ENABLED on both routers, because the
+# alternative -- `set interfaces pppoe pppoe0 disable` -- unlinks
+# /etc/ppp/peers/pppoe0 (interfaces_pppoe.py treats `disable` and `delete`
+# identically), and pppd's options file IS that path. A promotion then had to
+# re-render it via a full config commit at priority 322, where one unrelated
+# invalid node fails the whole commit and takes the 10 gig down with it. It also
+# made op-mode `connect interface pppoe0` unusable, since that refuses when the
+# peers file is absent.
+#
+# With the node enabled, interfaces_pppoe.py's apply() does this on EVERY commit
+# that touches the pppoe subtree:
+#
+#     if not is_systemd_service_running('ppp@pppoe0.service') or shutdown_required:
+#         call('systemctl restart ppp@pppoe0.service')
+#
+# -- i.e. the backup actively tries to dial whenever anything commits. A
+# `pulumi up`, a `sim-net-apply.sh apply`, or the boot-time config load are all
+# that commit. This gate is what makes that a no-op.
+#
+# /run is tmpfs, so the gate is shut at boot on both boxes and neither can dial
+# before VRRP has decided. ppp@.service is already After=vyos-router.service, so
+# no extra ordering is needed.
+[Unit]
+# Both must hold; multiple ConditionPathExists are ANDed.
+#   may-dial       -- vrrp-wan-reconcile has blessed this box (a renewed lease)
+#   /etc/ppp/peers -- refuse to start pppd against a missing options file, which
+#                     is what produced a restart loop of 47 and counting on
+#                     2026-09-05. A failed Condition is NOT a failure: the job
+#                     succeeds, the unit stays inactive, and `systemctl start`
+#                     exits 0 -- so callers must check is-active, never rc.
+ConditionPathExists=/run/vrrp-wan/may-dial
+ConditionPathExists=/etc/ppp/peers/pppoe0
+
+# Belt to that brace. The stock unit is Restart=on-failure/RestartSec=5s against
+# systemd's default StartLimitIntervalSec=10s/Burst=5 -- two restarts per window,
+# so the limiter can never trip and a doomed pppd retries for ever.
+StartLimitIntervalSec=600
+StartLimitBurst=6
+
+[Service]
+RestartSec=15
+# A hung pppd must be resolved inside the failover budget. The stock 90s means a
+# demoted router could still hold the session while the new master is dialling.
+# 20s still allows a clean LCP Terminate + PADT in the normal case.
+TimeoutStopSec=20

migration/pulumi-override-he-tunnel-both.json

@@ -0,0 +1,188 @@
+{
+  "id": "he-ipv6-tunnel",
+  "reason": "6in4 tunnel to Hurricane Electric, bringing 2001:470:187e::/48 in, on BOTH routers. SUPERSEDES he-ipv6-tunnel-vyos001, whose reason said 'vyos002 carries bond0.53 disabled, so the source address does not exist there and the tunnel would simply stay down -- adding it there is for a later takeover story, not now.' Both halves of that expired on 2026-09-06. `vif 53 disable` is no longer a property of vyos002: it is RUNTIME state owned by vrrp-wan-reconcile, keyed on who holds the management VIP, and deliberately absent from this model (see pppoe-gated-not-config-disabled and PPPOE-HA.md). And the takeover story shipped -- a drill moved the WAN and back, 52s and 36s. IPv6 did not follow it, so every failover took the whole v6 estate down for as long as vyos002 held the VIP. WHY THIS IS CHEAP: 87.192.101.48 is the 10 gig lease bound to the cloned MAC, and the drill proved the ISP re-issues THE SAME address to that MAC on the other router's port. The tunnel endpoint is therefore stable across the pair, so a router-level failover needs no HE API call at all -- only the tunnel present on both boxes and live on exactly one. HE updates remain solely for the within-box fall back to PPPoE, which /config/he-tunnel-follow already handles. WHY THE RUNTIME GATE IS LOAD-BEARING, not a nicety: measured in labsim 2026-09-06, VyOS ACCEPTS a tunnel whose source-address does not exist on the box (commit rc=0) and brings the link UP anyway. It is a blackhole that will happily attract the v6 default route -- not the inert node the old reason assumed. vrrp-wan-reconcile holds tun0 down on the backup and brings it up on the master, at kernel level, with no commit in the failover path. Verified in the sim: backup tun=DOWN radvd=inactive, master tun=UP radvd=active. MTU 1480, not 1500: 6in4 adds a 20-byte outer IPv4 header. Leave it at 1500 and IPv6 appears to work while large transfers hang. The RA link-mtu is 1472 -- the PPPoE figure -- deliberately, on BOTH routers: it cannot be reconciled at runtime because it needs a commit, so advertise the lower of the two paths and be correct on either WAN. Production previously pinned 1480 and was silently wrong whenever the WAN fell back. bond0.9 takes ::1 on vyos001 and ::2 on vyos002 -- NOT the same address: SLAAC hosts take their gateway from the advertising router's link-local, so the global address need not move, and duplicating it would only produce a DAD conflict. default-preference is high on vyos001 and low on vyos002 so that if both ever advertise at once -- radvd's config is rendered into /run and a booting backup starts it before VRRP has decided -- hosts prefer the normal master, while a genuinely dead vyos001 still leaves vyos002 as the only router on the link. No firewall change is needed: the IPv6 firewall accepts only from interface-group LAN, so tun0 is untrusted by default. It is already default-deny on BOTH routers -- that ordering held. REHEARSAL: labsim/labsim-he-endpoint.sh now builds a fake HE endpoint and stub tunnelbroker API, closing the 'the sim has no public IPv4 and no HE endpoint' gap the old reason cited as why this was never tested. labsim/labsim-ipv6-ha-test.sh is the matrix. Mechanism proven there; the end-to-end v6 datapath is not yet, because the sim's inter-island transit crosses libvirt NAT -- see that file's KNOWN SIM GAP header.",
+  "set": [
+    {
+      "path": [
+        "interfaces",
+        "tunnel",
+        "tun0",
+        "encapsulation"
+      ],
+      "value": "sit"
+    },
+    {
+      "path": [
+        "interfaces",
+        "tunnel",
+        "tun0",
+        "source-address"
+      ],
+      "value": "87.192.101.48"
+    },
+    {
+      "path": [
+        "interfaces",
+        "tunnel",
+        "tun0",
+        "remote"
+      ],
+      "value": "216.66.88.98"
+    },
+    {
+      "path": [
+        "interfaces",
+        "tunnel",
+        "tun0",
+        "address"
+      ],
+      "value": "2001:470:1f1c:f6::2/64"
+    },
+    {
+      "path": [
+        "interfaces",
+        "tunnel",
+        "tun0",
+        "mtu"
+      ],
+      "value": "1480"
+    },
+    {
+      "path": [
+        "interfaces",
+        "tunnel",
+        "tun0",
+        "description"
+      ],
+      "value": "HE 6in4 tunnel - 2001:470:187e::/48"
+    },
+    {
+      "path": [
+        "protocols",
+        "static",
+        "route6",
+        "::/0",
+        "next-hop",
+        "2001:470:1f1c:f6::1"
+      ],
+      "value": {}
+    },
+    {
+      "path": [
+        "system",
+        "task-scheduler",
+        "task",
+        "he-tunnel-follow",
+        "executable",
+        "path"
+      ],
+      "value": "/config/he-tunnel-follow"
+    },
+    {
+      "path": [
+        "system",
+        "task-scheduler",
+        "task",
+        "he-tunnel-follow",
+        "executable",
+        "arguments"
+      ],
+      "value": "run"
+    },
+    {
+      "path": [
+        "system",
+        "task-scheduler",
+        "task",
+        "he-tunnel-follow",
+        "interval"
+      ],
+      "value": "1m"
+    }
+  ],
+  "perRouter": {
+    "vyos001": [
+      {
+        "path": [
+          "interfaces",
+          "bonding",
+          "bond0",
+          "vif",
+          "9",
+          "address"
+        ],
+        "value": "2001:470:187e:9::1/64"
+      },
+      {
+        "path": [
+          "service",
+          "router-advert",
+          "interface",
+          "bond0.9",
+          "default-preference"
+        ],
+        "value": "high"
+      }
+    ],
+    "vyos002": [
+      {
+        "path": [
+          "interfaces",
+          "bonding",
+          "bond0",
+          "vif",
+          "9",
+          "address"
+        ],
+        "value": "2001:470:187e:9::2/64"
+      },
+      {
+        "path": [
+          "service",
+          "router-advert",
+          "interface",
+          "bond0.9",
+          "default-preference"
+        ],
+        "value": "low"
+      }
+    ]
+  },
+  "sharedRouterAdvert": [
+    {
+      "path": [
+        "service",
+        "router-advert",
+        "interface",
+        "bond0.9",
+        "link-mtu"
+      ],
+      "value": "1472"
+    },
+    {
+      "path": [
+        "service",
+        "router-advert",
+        "interface",
+        "bond0.9",
+        "prefix",
+        "2001:470:187e:9::/64",
+        "preferred-lifetime"
+      ],
+      "value": "604800"
+    },
+    {
+      "path": [
+        "service",
+        "router-advert",
+        "interface",
+        "bond0.9",
+        "prefix",
+        "2001:470:187e:9::/64",
+        "valid-lifetime"
+      ],
+      "value": "2592000"
+    }
+  ],
+  "_staging_note": "MERGED 2026-09-06 as kubernetes-deployment@6d4e080 on main. This file is now only a historical record; the live model is infra/vyos/subtrees/overrides.json, where the four IPv6 overrides (he-ipv6-tunnel, he-tunnel-follow-scheduler, firewall-accept-he-6in4, ipv6-vlan9-private + ipv6-vlan9-addr-vyos00[12]) are scoped to both routers. vyos:verify reports 533/534 nodes, zero drift. TWO THINGS THE MERGE ITSELF CAUGHT, worth carrying: (1) firewall-accept-he-6in4 was vyos001-only, so vyos002 had no proto-41 accept under its IPv4 input default-deny -- a failover would have left tun0 up and radvd running on the new master while HE's encapsulated traffic was dropped by its own firewall. The tunnel deployment alone was NOT sufficient. (2) The per-router bond0.9 override must list the IPv4 address next to the IPv6 one, because an override set declares the COMPLETE set for its path. Also: do not stage vyos model changes on a feature branch. The first attempt at this merge was made on fix/openbao-preview-blockers, which is 15 commits behind main and predates the PPPoE HA overrides -- committing it would have reverted pppoe-gated-not-config-disabled and vrrp-transition-scripts-wan-follows-master. main lives in the .worktrees/grafana-token worktree."
+}

migration/pulumi-override-pppoe-gated.json

@@ -0,0 +1,55 @@
+{
+  "_comment": [
+    "STAGED, NOT APPLIED. Paste these two objects into",
+    "kubernetes-deployment infra/vyos/subtrees/overrides.json -- but ONLY after",
+    "migration/vrrp-wan-install has run on BOTH production routers.",
+    "",
+    "Ordering is not a nicety. Another agent runs `pulumi up` on that repo, so",
+    "merging this file IS a production change, made by someone else, at a time",
+    "you do not choose. Removing `interfaces pppoe pppoe0 disable` from vyos002",
+    "before the gate exists there lets vyos002 dial the moment anything commits,",
+    "and Vodafone is a single-session account: it would take the live session off",
+    "vyos001 and drop the household's internet.",
+    "",
+    "Install the gate first. Verify `systemctl show ppp@pppoe0 -p ConditionResult`",
+    "reads `no` on vyos002. Only then merge.",
+    "",
+    "Note there is deliberately NO override asserting `vif 53 disable`.",
+    "applyTree is delete-then-set per subtree, so the model is authoritative and",
+    "omission means deletion -- but the 10 gig resting state is RUNTIME state",
+    "owned by vrrp-wan-reconcile, keyed on who holds the management VIP. Pinning",
+    "it in the model would fight the reconciler on every apply. The rule is",
+    "`npm run vyos:export && npm run vyos:render` immediately before any",
+    "`pulumi up`, so the model follows whichever router actually holds the WAN."
+  ],
+  "overrides": [
+    {
+      "id": "pppoe-gated-not-config-disabled",
+      "routers": ["vyos002"],
+      "reason": "PPPoE cannot live on the VyOS config plane. interfaces_pppoe.py treats `disable` and `delete` identically: both unlink /etc/ppp/peers/pppoe0, which is pppd's own options file (ExecStart=/usr/sbin/pppd call %I), call PPPoEIf.remove() to withdraw the FRR default route, and stop the unit. So the resting state destroyed exactly what the promotion path needed, and ppp@pppoe0 restart-looped against the missing file -- 47 restarts observed, zero sessions at the access concentrator -- without ever tripping systemd's limiter, because RestartSec=5s against the default 10s/5-burst window is only two restarts per interval. It also made op-mode `connect interface pppoe0` unusable and put every failover behind a priority-322 commit where one unrelated invalid node fails the whole thing. pppoe0 is now ENABLED on both routers so the peers file always exists, and dialling is gated by ppp@pppoe0.service.d/10-vrrp-wan-gate.conf on /run/vrrp-wan/may-dial, a lease renewed by vrrp-wan-reconcile and revoked by vrrp-wan-guard. /run is tmpfs, so the gate is shut at boot and neither box dials before VRRP has decided. This override encodes must-never-come-back: a re-run of migration/vyos-mode-delta.py or a stale import must not re-pin `disable`. PREREQUISITE: the gate drop-in must already be installed on vyos002, or removing `disable` lets it dial and steal the single ISP session. Proven in labsim across session-control replace/deny/disable; see lab migration/PPPOE-HA.md.",
+      "remove": [["interfaces", "pppoe", "pppoe0", "disable"]]
+    },
+    {
+      "id": "vrrp-transition-scripts-wan-follows-master",
+      "reason": "Gives the WAN a fast path on top of the 30s reconcile timer. Both hooks exec the same reconciler -- one code path, asked at different moments -- so a lost or duplicated transition cannot desynchronise anything; the timer remains the correctness guarantee and the scripts are only latency. `stop` and `fault` matter as much as `backup`: a stopped keepalived is a demotion too, and without those a box would keep the WAN while holding no VIPs, which is the 2026-09-02 outage shape. They go on the SYNC GROUP because VyOS refuses a per-group script while the group is in a sync group. Do not rely on these alone: on 2026-09-02 keepalived-fifo.py logged NOTHING for a promotion while Keepalived_vrrp logged all six instances entering MASTER, which is precisely why the reconcile timer exists.",
+      "set": [
+        {
+          "path": ["high-availability", "vrrp", "sync-group", "MAIN", "transition-script", "master"],
+          "value": "/config/vrrp-wan-take"
+        },
+        {
+          "path": ["high-availability", "vrrp", "sync-group", "MAIN", "transition-script", "backup"],
+          "value": "/config/vrrp-wan-release"
+        },
+        {
+          "path": ["high-availability", "vrrp", "sync-group", "MAIN", "transition-script", "fault"],
+          "value": "/config/vrrp-wan-release"
+        },
+        {
+          "path": ["high-availability", "vrrp", "sync-group", "MAIN", "transition-script", "stop"],
+          "value": "/config/vrrp-wan-release"
+        }
+      ]
+    }
+  ]
+}

migration/unifi-export.py

@@ -0,0 +1,335 @@
+#!/usr/bin/env python3
+"""Export everything from the UniFi controller that the VyOS cutover must preserve.
+
+The point is that nothing quietly stops working after the switch. That means
+capturing not just the networks but every DHCP reservation, every port forward
+and every firewall rule — the things nobody remembers configuring until they
+break.
+
+Writes one JSON file per endpoint into ./export/ (raw, unmodified — the source
+of truth) plus inventory.json, a normalised view used by the VyOS generator.
+
+  ./unifi-export.py                 # export to ./export/
+  ./unifi-export.py --out /tmp/x    # elsewhere
+  ./unifi-export.py --summary       # print a human summary of what was found
+
+WARNING: the raw export contains secrets (wlanconf holds WiFi passphrases,
+setting holds RADIUS/auth material). ./export/ is gitignored — keep it that way.
+"""
+from __future__ import annotations
+
+import argparse
+import ipaddress
+import json
+import os
+import sys
+
+import _unifi
+
+# endpoint -> why it matters for the cutover
+ENDPOINTS = {
+    "rest/networkconf": "networks: VLANs, subnets, DHCP ranges, DNS, lease time",
+    "rest/user":        "known clients — this is where fixed DHCP reservations live",
+    "stat/sta":         "currently active clients and their live IPs",
+    "rest/firewallrule": "firewall rules",
+    "rest/firewallgroup": "address/port groups referenced by rules",
+    "rest/portforward": "port forwards (inbound NAT)",
+    "rest/routing":     "static routes",
+    "rest/dhcpoption":  "custom DHCP options",
+    "rest/wlanconf":    "wireless networks (VLAN bindings)",
+    "stat/device":      "switches/APs incl. per-port VLAN config",
+    "rest/setting":     "controller settings (incl. USG/gateway config)",
+    "rest/usergroup":   "bandwidth groups referenced by clients",
+    "rest/dynamicdns":  "dynamic DNS",
+}
+
+
+def build_inventory(raw: dict) -> dict:
+    """Normalise the parts a migration actually has to reproduce."""
+    nets_by_id = {n["_id"]: n for n in raw.get("rest/networkconf", []) if isinstance(n, dict)}
+
+    networks = []
+    for n in raw.get("rest/networkconf", []):
+        if not isinstance(n, dict):
+            continue
+        networks.append({
+            "id": n.get("_id"),
+            "name": n.get("name"),
+            "purpose": n.get("purpose"),
+            "vlan": n.get("vlan"),
+            "vlan_enabled": n.get("vlan_enabled"),
+            "subnet": n.get("ip_subnet"),
+            "domain_name": n.get("domain_name"),
+            "dhcp_enabled": n.get("dhcpd_enabled"),
+            "dhcp_start": n.get("dhcpd_start"),
+            "dhcp_stop": n.get("dhcpd_stop"),
+            "dhcp_lease": n.get("dhcpd_leasetime"),
+            "dhcp_dns": [n.get(f"dhcpd_dns_{i}") for i in (1, 2, 3, 4) if n.get(f"dhcpd_dns_{i}")],
+            "dhcp_gateway": n.get("dhcpd_gateway") or n.get("dhcpd_gateway_enabled"),
+            "dhcp_ntp": [n.get(f"dhcpd_ntp_{i}") for i in (1, 2) if n.get(f"dhcpd_ntp_{i}")],
+            "igmp_snooping": n.get("igmp_snooping"),
+            "enabled": n.get("enabled", True),
+        })
+
+    # ip_subnet is the GATEWAY address with a prefix ("10.0.0.1/23"), not the
+    # network address — so derive the real subnet before matching against it.
+    subnets = []
+    for n in networks:
+        if not n["subnet"]:
+            continue
+        try:
+            iface = ipaddress.ip_interface(n["subnet"])
+        except ValueError:
+            continue
+        subnets.append((iface.network, n))
+
+    def resolve_net(ip: str | None, network_id: str | None) -> dict:
+        """Which network does this reservation belong to?
+
+        Most reservations here (23 of 31 as of the first export) carry no
+        network_id at all — UniFi simply does not bind them. VyOS needs the
+        subnet to place a static-mapping, so fall back to containment.
+        """
+        if network_id and network_id in nets_by_id:
+            nid = nets_by_id[network_id]
+            return {"name": nid.get("name"), "vlan": nid.get("vlan"), "by": "network_id"}
+        if ip:
+            try:
+                addr = ipaddress.ip_address(ip)
+            except ValueError:
+                return {"name": None, "vlan": None, "by": "unresolved"}
+            for net, meta in subnets:
+                if addr in net:
+                    return {"name": meta["name"], "vlan": meta["vlan"], "by": "subnet"}
+        return {"name": None, "vlan": None, "by": "unresolved"}
+
+    # Fixed reservations: the single most important thing to carry over, and
+    # the easiest to lose — nobody has these written down anywhere else.
+    reservations = []
+    for u in raw.get("rest/user", []):
+        if not isinstance(u, dict) or not u.get("use_fixedip"):
+            continue
+        net = resolve_net(u.get("fixed_ip"), u.get("network_id"))
+        reservations.append({
+            "mac": (u.get("mac") or "").lower(),
+            "ip": u.get("fixed_ip"),
+            "name": u.get("name") or u.get("hostname") or "",
+            "hostname": u.get("hostname") or "",
+            "network_id": u.get("network_id"),
+            "network_name": net["name"],
+            "network_vlan": net["vlan"],
+            "resolved_by": net["by"],
+            "note": (u.get("note") or "").strip(),
+        })
+    reservations.sort(key=lambda r: tuple(int(p) for p in r["ip"].split(".")) if r["ip"] else (0,))
+
+    # Active leases without a reservation: these devices work today by luck of
+    # the lease database. After a DHCP server swap they get a NEW address.
+    reserved_macs = {r["mac"] for r in reservations}
+    dynamic = []
+    for c in raw.get("stat/sta", []):
+        if not isinstance(c, dict):
+            continue
+        mac = (c.get("mac") or "").lower()
+        if mac in reserved_macs or not c.get("ip"):
+            continue
+        dynamic.append({
+            "mac": mac,
+            "ip": c.get("ip"),
+            "name": c.get("name") or c.get("hostname") or "",
+            "network": c.get("network"),
+        })
+    dynamic.sort(key=lambda r: tuple(int(p) for p in r["ip"].split(".")) if r["ip"] else (0,))
+
+    port_forwards = [{
+        "name": p.get("name"), "enabled": p.get("enabled"),
+        "proto": p.get("proto"), "src": p.get("src"),
+        "dst_port": p.get("dst_port"), "fwd": p.get("fwd"),
+        "fwd_port": p.get("fwd_port"), "log": p.get("log"),
+    } for p in raw.get("rest/portforward", []) if isinstance(p, dict)]
+
+    firewall_rules = [{
+        "name": r.get("name"), "enabled": r.get("enabled"), "action": r.get("action"),
+        "ruleset": r.get("ruleset"), "rule_index": r.get("rule_index"),
+        "protocol": r.get("protocol"),
+        "src_address": r.get("src_address"), "dst_address": r.get("dst_address"),
+        "src_firewallgroup_ids": r.get("src_firewallgroup_ids"),
+        "dst_firewallgroup_ids": r.get("dst_firewallgroup_ids"),
+        "src_networkconf_id": r.get("src_networkconf_id"),
+        "dst_networkconf_id": r.get("dst_networkconf_id"),
+    } for r in raw.get("rest/firewallrule", []) if isinstance(r, dict)]
+
+    firewall_groups = [{
+        "id": g.get("_id"), "name": g.get("name"),
+        "type": g.get("group_type"), "members": g.get("group_members"),
+    } for g in raw.get("rest/firewallgroup", []) if isinstance(g, dict)]
+
+    static_routes = [{
+        "name": r.get("name"), "enabled": r.get("enabled"),
+        "network": r.get("static-route_network"),
+        "nexthop": r.get("static-route_nexthop"),
+        "distance": r.get("static-route_distance"),
+        "type": r.get("static-route_type"),
+    } for r in raw.get("rest/routing", []) if isinstance(r, dict)]
+
+    return {
+        "networks": networks,
+        "reservations": reservations,
+        "dynamic_clients": dynamic,
+        "port_forwards": port_forwards,
+        "firewall_rules": firewall_rules,
+        "firewall_groups": firewall_groups,
+        "static_routes": static_routes,
+        "warnings": find_warnings(networks, reservations),
+    }
+
+
+def find_warnings(networks: list, reservations: list) -> list:
+    """Things that are fine under UniFi but bite when rebuilt on VyOS."""
+    warns = []
+
+    for n in networks:
+        if not n["subnet"]:
+            continue
+        try:
+            iface = ipaddress.ip_interface(n["subnet"])
+        except ValueError:
+            warns.append({"kind": "bad_subnet", "network": n["name"], "detail": n["subnet"]})
+            continue
+        # UniFi stores the gateway in ip_subnet. A gateway equal to the network
+        # address is legal in a /23 but plenty of tooling rejects it, so it must
+        # not be discovered during the cutover window.
+        if iface.ip == iface.network.network_address:
+            warns.append({
+                "kind": "gateway_is_network_address", "network": n["name"],
+                "detail": f"gateway {iface.ip} is the network address of {iface.network}",
+            })
+
+    # Reservations that sit inside the dynamic pool. UniFi's dhcpd tolerates
+    # this; whether VyOS does depends on its DHCP backend, so every one of these
+    # is a config that must be proven on the sim before cutover.
+    ranges = []
+    for n in networks:
+        if n["dhcp_enabled"] and n["dhcp_start"] and n["dhcp_stop"]:
+            try:
+                ranges.append((n["name"], ipaddress.ip_address(n["dhcp_start"]),
+                               ipaddress.ip_address(n["dhcp_stop"])))
+            except ValueError:
+                pass
+    inside = []
+    for r in reservations:
+        if not r["ip"]:
+            continue
+        try:
+            addr = ipaddress.ip_address(r["ip"])
+        except ValueError:
+            continue
+        for name, lo, hi in ranges:
+            if lo <= addr <= hi:
+                inside.append(f"{r['ip']} ({r['name'] or r['mac']}) in {name} pool")
+                break
+    if inside:
+        warns.append({"kind": "reservation_inside_dhcp_pool",
+                      "count": len(inside), "detail": inside})
+
+    unresolved = [f"{r['ip']} {r['mac']} {r['name']}"
+                  for r in reservations if r["resolved_by"] == "unresolved"]
+    if unresolved:
+        warns.append({"kind": "reservation_matches_no_subnet",
+                      "count": len(unresolved), "detail": unresolved})
+    return warns
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--out", default=os.path.join(os.path.dirname(os.path.abspath(__file__)), "export"))
+    ap.add_argument("--summary", action="store_true")
+    args = ap.parse_args()
+
+    os.makedirs(args.out, exist_ok=True)
+    opener, base, site = _unifi.client()
+    print(f"controller {base}  site {site}")
+
+    raw: dict = {}
+    errors = []
+    for path, why in ENDPOINTS.items():
+        data = _unifi.get(opener, base, site, path)
+        if isinstance(data, dict) and "__error__" in data:
+            errors.append((path, data["__error__"]))
+            print(f"  {path:22} FAILED  {data['__error__'][:50]}")
+            continue
+        raw[path] = data
+        fname = path.replace("/", "_") + ".json"
+        with open(os.path.join(args.out, fname), "w") as fh:
+            json.dump(data, fh, indent=2, sort_keys=True)
+        print(f"  {path:22} {len(data):4d}  -> {fname}")
+
+    inventory = build_inventory(raw)
+    with open(os.path.join(args.out, "inventory.json"), "w") as fh:
+        json.dump(inventory, fh, indent=2, sort_keys=True)
+
+    print(f"\nwrote {args.out}/inventory.json")
+    print(f"  networks           {len(inventory['networks'])}")
+    print(f"  DHCP reservations  {len(inventory['reservations'])}")
+    print(f"  dynamic clients    {len(inventory['dynamic_clients'])}  (no reservation — see summary)")
+    print(f"  port forwards      {len(inventory['port_forwards'])}")
+    print(f"  firewall rules     {len(inventory['firewall_rules'])}")
+    print(f"  static routes      {len(inventory['static_routes'])}")
+    if errors:
+        print(f"  endpoints failed   {len(errors)}: {[e[0] for e in errors]}")
+
+    if args.summary:
+        print_summary(inventory)
+    return 0
+
+
+def print_summary(inv: dict) -> None:
+    print("\n=== networks ===")
+    print(f"{'name':22} {'vlan':>5}  {'subnet':20} {'dhcp range':32} lease")
+    for n in sorted(inv["networks"], key=lambda x: (x["vlan"] or 0)):
+        rng = f"{n['dhcp_start']} - {n['dhcp_stop']}" if n["dhcp_enabled"] else "(dhcp off)"
+        print(f"{(n['name'] or '')[:22]:22} {str(n['vlan'] or '-'):>5}  "
+              f"{(n['subnet'] or '-'):20} {rng:32} {n['dhcp_lease'] or '-'}")
+
+    print(f"\n=== DHCP reservations ({len(inv['reservations'])}) ===")
+    for r in inv["reservations"]:
+        print(f"  {r['ip']:16} {r['mac']:18} {(r['network_name'] or '?')[:14]:14} {r['name'][:30]}")
+
+    if inv["port_forwards"]:
+        print(f"\n=== port forwards ({len(inv['port_forwards'])}) ===")
+        for p in inv["port_forwards"]:
+            state = "" if p["enabled"] else "  [DISABLED]"
+            print(f"  {p['proto']:6} {str(p['src']):16}:{str(p['dst_port']):11} -> "
+                  f"{p['fwd']}:{p['fwd_port']}   {p['name']}{state}")
+
+    if inv["firewall_rules"]:
+        print(f"\n=== firewall rules ({len(inv['firewall_rules'])}) ===")
+        for r in inv["firewall_rules"]:
+            state = "" if r["enabled"] else "  [DISABLED]"
+            print(f"  {str(r['ruleset']):22} {str(r['action']):8} {r['name']}{state}")
+
+    if inv["warnings"]:
+        print(f"\n=== {len(inv['warnings'])} things to settle before cutover ===")
+        for w in inv["warnings"]:
+            n = w.get("count")
+            print(f"  [{w['kind']}]" + (f"  x{n}" if n else ""))
+            det = w["detail"]
+            for line in (det if isinstance(det, list) else [det])[:6]:
+                print(f"      {line}")
+            if isinstance(det, list) and len(det) > 6:
+                print(f"      ... and {len(det) - 6} more (see inventory.json)")
+
+    n_dyn = len(inv["dynamic_clients"])
+    if n_dyn:
+        print(f"\n=== {n_dyn} active clients WITHOUT a reservation ===")
+        print("  These hold their address only via the current lease database. A DHCP")
+        print("  server swap hands them a different one — fine for phones, not fine for")
+        print("  anything another host reaches by IP. Review before cutover:")
+        for c in inv["dynamic_clients"][:40]:
+            print(f"  {c['ip']:16} {c['mac']:18} {(c['network'] or '')[:14]:14} {c['name'][:30]}")
+        if n_dyn > 40:
+            print(f"  ... and {n_dyn - 40} more (see inventory.json)")
+
+
+if __name__ == "__main__":
+    sys.exit(main())

migration/unifi-reserve-all.py

@@ -0,0 +1,236 @@
+#!/usr/bin/env python3
+"""Reserve every active client at the address it already has.
+
+Why this exists: kea does not inherit UniFi's lease database. At cutover it
+starts with an empty view of who holds what, so it can hand an address that is
+currently in use to a different device. Reservations are what carry "this
+device has this address" across the switch, because they live in config rather
+than in lease state.
+
+Dry run by default -- this writes to the live controller, and 40-odd writes is
+not something to trigger by accident.
+
+  ./unifi-reserve-all.py                  # show the plan, change nothing
+  ./unifi-reserve-all.py --apply          # write them
+  ./unifi-reserve-all.py --skip-random    # omit randomised/private MACs
+
+Only clients on networks that actually run DHCP are considered, which
+automatically excludes WAN transit VLANs where a reservation is meaningless.
+Anything already reserved is left alone, and an address already reserved to a
+different MAC is reported and skipped rather than stolen.
+"""
+from __future__ import annotations
+
+import argparse
+import ipaddress
+import sys
+
+import _unifi
+
+# The VRRP virtual addresses, read from `show configuration commands` on
+# vyos001. UniFi sees these as ordinary client addresses because the firewalls'
+# bond MACs answer for them, and their reported IP flips between the real
+# interface address and the VIP. Reserving one would put a DHCP reservation on
+# the gateway address itself.
+VIPS = {
+    "192.168.1.254", "192.168.9.254", "192.168.3.254",
+    "10.0.9.254", "10.0.1.254", "192.168.2.254",
+}
+
+# Every MAC the two firewalls own (bond0/eth0/eth1 share one, eth2 and eth3
+# have their own). These interfaces are statically configured routers, not DHCP
+# clients -- except eth2, which is deliberately reserved and already handled.
+ROUTER_MACS = {
+    "64:62:66:25:96:45", "64:62:66:25:96:46", "64:62:66:25:96:48",  # vyos001
+    "64:62:66:25:96:51", "64:62:66:25:96:52", "64:62:66:25:96:54",  # vyos002
+}
+
+
+def is_random_mac(mac: str) -> bool:
+    """Locally-administered bit set => a privacy/randomised MAC.
+
+    Worth calling out: such a device re-randomises periodically, so the
+    reservation stops matching it and becomes dead config. Harmless, but it
+    will never do what it looks like it does.
+    """
+    try:
+        return bool(int(mac.split(":")[0], 16) & 0x02)
+    except (ValueError, IndexError):
+        return False
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--apply", action="store_true", help="actually write (default: dry run)")
+    ap.add_argument("--skip-random", action="store_true", help="omit randomised MACs")
+    ap.add_argument("--plan", default="reservation-plan.tsv",
+                    help="dry run WRITES this file; --apply READS it and applies "
+                         "exactly what it contains")
+    args = ap.parse_args()
+
+    opener, base, site = _unifi.client()
+    users = _unifi.get(opener, base, site, "rest/user")
+    nets = _unifi.get(opener, base, site, "rest/networkconf")
+    sta = _unifi.get(opener, base, site, "stat/sta")
+    for blob in (users, nets, sta):
+        if isinstance(blob, dict):
+            print(f"error reading controller: {blob['__error__']}", file=sys.stderr)
+            return 1
+
+    # Only networks that serve DHCP: a reservation on a WAN transit VLAN means
+    # nothing, and those are exactly the ones without dhcpd_enabled.
+    serving = []
+    for n in nets:
+        if not (n.get("dhcpd_enabled") and n.get("ip_subnet")):
+            continue
+        try:
+            serving.append((ipaddress.ip_interface(n["ip_subnet"]).network, n))
+        except ValueError:
+            continue
+
+    by_mac = {(u.get("mac") or "").lower(): u for u in users}
+    taken = {u.get("fixed_ip"): (u.get("mac") or "").lower()
+             for u in users if u.get("use_fixedip")}
+
+    plan, skipped = [], []
+    for c in sta:
+        mac, ip = (c.get("mac") or "").lower(), c.get("ip")
+        if not mac or not ip:
+            continue
+        label = c.get("name") or c.get("hostname") or "?"
+        user = by_mac.get(mac)
+
+        if ip in VIPS:
+            skipped.append((ip, mac, label, "VRRP virtual address - not a client"))
+            continue
+        if mac in ROUTER_MACS:
+            skipped.append((ip, mac, label, "firewall's own interface - statically configured"))
+            continue
+
+        net = next((n for netw, n in serving if ipaddress.ip_address(ip) in netw), None)
+        if net is None:
+            skipped.append((ip, mac, label, "not on a DHCP-serving network"))
+            continue
+        # The gateway is the router, not a lease.
+        if ip == str(ipaddress.ip_interface(net["ip_subnet"]).ip):
+            skipped.append((ip, mac, label, "network gateway address"))
+            continue
+        if user is None:
+            skipped.append((ip, mac, label, "not a known client on the controller"))
+            continue
+        if user.get("use_fixedip"):
+            if user.get("fixed_ip") != ip:
+                skipped.append((ip, mac, label,
+                                f"already reserved at {user.get('fixed_ip')} - left alone"))
+            continue
+        if ip in taken and taken[ip] != mac:
+            skipped.append((ip, mac, label,
+                            f"address already reserved to {taken[ip]}"))
+            continue
+        if args.skip_random and is_random_mac(mac):
+            skipped.append((ip, mac, label, "randomised MAC (--skip-random)"))
+            continue
+        plan.append((ip, mac, label, user, net))
+
+    # Generic safety net: if two MACs report the same current address, at most
+    # one of them can legitimately keep it and we cannot tell which. Drop both
+    # and say so -- this is exactly how the VRRP VIPs first showed up.
+    counts: dict[str, int] = {}
+    for ip, *_ in plan:
+        counts[ip] = counts.get(ip, 0) + 1
+    contested = {ip for ip, n in counts.items() if n > 1}
+    if contested:
+        for ip, mac, label, _u, _n in [p for p in plan if p[0] in contested]:
+            skipped.append((ip, mac, label, "address claimed by more than one MAC"))
+        plan = [p for p in plan if p[0] not in contested]
+
+    plan.sort(key=lambda r: ipaddress.ip_address(r[0]))
+
+    print(f"=== plan: {len(plan)} new reservation(s) ===")
+    for ip, mac, label, _u, net in plan:
+        flag = "  [randomised MAC]" if is_random_mac(mac) else ""
+        print(f"  {ip:16} {mac:18} {label[:28]:28} {net.get('name')}{flag}")
+    if skipped:
+        print(f"\n=== skipped ({len(skipped)}) ===")
+        for ip, mac, label, why in sorted(skipped):
+            print(f"  {ip:16} {mac:18} {label[:24]:24} {why}")
+
+    n_rand = sum(1 for p in plan if is_random_mac(p[1]))
+    if n_rand:
+        print(f"\nnote: {n_rand} of these use randomised MACs. The reservation "
+              f"stops matching once the device re-randomises.")
+
+    if not args.apply:
+        with open(args.plan, "w") as fh:
+            for ip, mac, label, _u, _n in plan:
+                fh.write(f"{mac}\t{ip}\t{label}\n")
+        print(f"\ndry run -- nothing written to the controller.")
+        print(f"plan saved to {args.plan}; re-run with --apply to apply exactly that.")
+        return 0
+
+    # Apply the plan that was REVIEWED, not one recomputed now.
+    #
+    # This cost a k8s node an outage. The apply used to re-read stat/sta, and a
+    # client that renewed between the dry run and the apply got pinned to
+    # whatever transient address it happened to hold at that instant -- worker1
+    # was reviewed at .13 and written as .242. A plan you looked at and a plan
+    # that gets applied must be the same object.
+    try:
+        with open(args.plan) as fh:
+            reviewed = {}
+            for line in fh:
+                parts = line.rstrip("\n").split("\t")
+                if len(parts) >= 2:
+                    reviewed[parts[0].lower()] = parts[1]
+    except OSError:
+        print(f"no plan at {args.plan}. Run without --apply first and review it.",
+              file=sys.stderr)
+        return 1
+
+    drifted = [(ip, mac) for ip, mac, _l, _u, _n in plan
+               if mac in reviewed and reviewed[mac] != ip]
+    for ip, mac in drifted:
+        print(f"  note: {mac} now reports {ip}, plan says {reviewed[mac]} -- "
+              f"applying the plan", file=sys.stderr)
+
+    plan = [(reviewed[mac], mac, label, user, net)
+            for ip, mac, label, user, net in plan if mac in reviewed]
+    print(f"applying {len(plan)} reservation(s) from {args.plan}")
+
+    print()
+    ok = fail = 0
+    for ip, mac, label, user, net in plan:
+        res = _unifi.put(opener, base, site, f"rest/user/{user['_id']}",
+                         {"use_fixedip": True, "fixed_ip": ip, "network_id": net["_id"]})
+        if isinstance(res, dict):
+            print(f"  FAILED {ip:16} {mac}  {res['__error__'][:70]}")
+            fail += 1
+        else:
+            ok += 1
+
+    # Read back rather than trusting the write responses.
+    after = _unifi.get(opener, base, site, "rest/user")
+    live = {(u.get("mac") or "").lower() for u in after if u.get("use_fixedip")}
+    verified = sum(1 for _ip, mac, _l, _u, _n in plan if mac in live)
+    print(f"\nwrote {ok}, failed {fail}, verified live {verified}/{len(plan)}")
+    print(f"total reservations on the controller now: "
+          f"{sum(1 for u in after if u.get('use_fixedip'))}")
+
+    # Writing the controller is only half the job. The gateway applies config
+    # on its own schedule, and a device running config from before these
+    # changes will hand out addresses that disagree with what the controller
+    # shows -- which is how a k8s node ended up unable to get any lease at all
+    # while the controller looked perfectly correct.
+    print("\nThe controller now disagrees with what the gateway is running.")
+    print("Push it to the device and wait for state to return to 'connected':")
+    print("  python3 -c \"import _unifi; o,b,s=_unifi.client(); "
+          "print(_unifi.post(o,b,s,'cmd/devmgr',"
+          "{'cmd':'force-provision','mac':'<gateway-mac>'}))\"")
+    print("Then verify a real DISCOVER is answered before trusting it:")
+    print("  ssh vyos@<fw> 'sudo nmap --script broadcast-dhcp-discover -e eth2 "
+          "--script-args broadcast-dhcp-discover.mac=<client-mac>'")
+    return 0 if fail == 0 and verified == len(plan) else 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())

migration/unifi-reserve.py

@@ -0,0 +1,106 @@
+#!/usr/bin/env python3
+"""Set a fixed-IP reservation in UniFi, so it cannot lease that address away.
+
+Written for the firewalls' management NICs: their addresses are pinned static
+on the VyOS side, but UniFi still owns the pool they sit in and would happily
+hand the same address to something else. A reservation closes that gap while
+the USG is still the DHCP server, and it keeps the management address identical
+in both cutover modes.
+
+  ./unifi-reserve.py 64:62:66:25:96:47 192.168.8.143
+  ./unifi-reserve.py --dry-run <mac> <ip>
+
+Idempotent: an existing, matching reservation is reported and left alone. This
+writes to the live controller, so it verifies by reading the record back rather
+than trusting the response.
+"""
+from __future__ import annotations
+
+import argparse
+import ipaddress
+import sys
+
+import _unifi
+
+
+def find_network(nets: list, ip: str) -> dict | None:
+    """Which configured network contains this address?
+
+    ip_subnet holds the gateway address with a prefix ("192.168.8.1/23"), so
+    the network has to be derived from it rather than compared directly.
+    """
+    addr = ipaddress.ip_address(ip)
+    for n in nets:
+        raw = n.get("ip_subnet")
+        if not raw:
+            continue
+        try:
+            if addr in ipaddress.ip_interface(raw).network:
+                return n
+        except ValueError:
+            continue
+    return None
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser()
+    ap.add_argument("mac")
+    ap.add_argument("ip")
+    ap.add_argument("--dry-run", action="store_true")
+    args = ap.parse_args()
+
+    mac = args.mac.lower().replace("-", ":")
+    ipaddress.ip_address(args.ip)  # fail early on a typo
+
+    opener, base, site = _unifi.client()
+    users = _unifi.get(opener, base, site, "rest/user")
+    nets = _unifi.get(opener, base, site, "rest/networkconf")
+    for blob in (users, nets):
+        if isinstance(blob, dict):
+            print(f"error reading controller: {blob['__error__']}", file=sys.stderr)
+            return 1
+
+    user = next((u for u in users if (u.get("mac") or "").lower() == mac), None)
+    if user is None:
+        print(f"{mac} is not a known client -- connect it once, or create it "
+              f"in the UI first", file=sys.stderr)
+        return 1
+
+    net = find_network(nets, args.ip)
+    if net is None:
+        print(f"no configured network contains {args.ip}", file=sys.stderr)
+        return 1
+
+    label = user.get("name") or user.get("hostname") or mac
+    if user.get("use_fixedip") and user.get("fixed_ip") == args.ip:
+        print(f"{label} ({mac}) already reserved at {args.ip} -- nothing to do")
+        return 0
+    if user.get("use_fixedip"):
+        print(f"WARNING: {label} currently reserved at {user.get('fixed_ip')}, "
+              f"changing to {args.ip}", file=sys.stderr)
+
+    print(f"{label} ({mac}) -> {args.ip} on '{net.get('name')}' (VLAN {net.get('vlan') or 'native'})")
+    if args.dry_run:
+        print("  --dry-run: not writing")
+        return 0
+
+    payload = {"use_fixedip": True, "fixed_ip": args.ip, "network_id": net["_id"]}
+    res = _unifi.put(opener, base, site, f"rest/user/{user['_id']}", payload)
+    if isinstance(res, dict):
+        print(f"  write failed: {res['__error__']}", file=sys.stderr)
+        return 1
+
+    # Read it back: the controller accepting a PUT is not proof it stored what
+    # we asked for.
+    after = _unifi.get(opener, base, site, "rest/user")
+    check = next((u for u in after if (u.get("mac") or "").lower() == mac), {})
+    if check.get("use_fixedip") and check.get("fixed_ip") == args.ip:
+        print(f"  verified: reservation is live")
+        return 0
+    print(f"  VERIFY FAILED: controller reports use_fixedip="
+          f"{check.get('use_fixedip')} fixed_ip={check.get('fixed_ip')}", file=sys.stderr)
+    return 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())

migration/unifi-to-vyos.py

@@ -0,0 +1,251 @@
+#!/usr/bin/env python3
+"""Turn the UniFi export into the VyOS config that replaces it.
+
+Scope is deliberately narrow: DHCP and DNS. Those are the services the USG owns
+that VyOS must reproduce byte-for-byte in behaviour, because getting them wrong
+means clients lose their addresses or their name resolution. Everything else
+either stays on UniFi (wireless), has no VyOS equivalent (user groups), or is
+hand-written because it is not in the export (WAN, NAT, VRRP).
+
+This is not a general UniFi-to-VyOS converter and should not grow into one.
+
+  ./unifi-to-vyos.py --mode prod          # the cutover artifact
+  ./unifi-to-vyos.py --mode sim           # same MACs, labsim addresses
+  ./unifi-to-vyos.py --mode prod --check  # counts only, no output
+
+Both modes come from one code path on purpose: the config proven in labsim and
+the config applied to the firewalls must not be able to drift apart.
+
+DNS note: UniFi hands out the gateway's own IP as resolver whenever a network
+has no explicit dhcpd_dns -- true for 5 of the 6 VLANs, verified by labmaster
+resolving against 192.168.8.1. So VyOS must run `service dns forwarding` or
+those VLANs lose DNS entirely at cutover. LoT's explicit 10.0.0.194 is preserved
+as-is.
+"""
+from __future__ import annotations
+
+import argparse
+import ipaddress
+import json
+import os
+import re
+import sys
+
+# Upstream resolvers for VyOS's own forwarder -- the same pair the USG used on
+# its WAN (wan_dns1/wan_dns2). The NAS at 10.0.0.194 is deliberately NOT here:
+# it is legacy for ad.itaz.eu, and those records now live in Cloudflare, so the
+# zone resolves publicly (verified: nas001.ad.itaz.eu and kvm-macstudio1 both
+# answer from 8.8.8.8). That means no conditional forward is needed and the NAS
+# is out of the DNS path entirely.
+UPSTREAM_DNS = ["8.8.8.8", "8.8.4.4"]
+
+# labsim equivalents, keyed by VLAN id. Only VLAN 10 needs a /23: every one of
+# the 31 reservations is in LoT, which spans 10.0.0.x and 10.0.1.x, and a /24
+# cannot represent that. k8s and Private are also /23 in production but hold no
+# reservations, so they keep their existing /24 and their DHCP range is clamped
+# (reported at generation time -- never silently).
+SIM_SUBNETS = {
+    1:   "172.31.1.0/24",
+    2:   "172.31.2.0/24",
+    3:   "172.31.3.0/24",
+    9:   "172.31.9.0/24",
+    10:  "172.31.10.0/23",
+    200: "172.31.200.0/24",
+}
+
+
+def vlan_of(net: dict) -> int:
+    """VLAN id, treating the untagged Management network as 1.
+
+    UniFi stores vlan=None for the native network; the VyOS side already uses
+    vrid 1 for it (high-availability group 'native'), so 1 is the consistent id.
+    """
+    return int(net["vlan"]) if net.get("vlan") else 1
+
+
+def sanitize(name: str, fallback: str) -> str:
+    """Reduce a UniFi client name to something VyOS will accept as a node name.
+
+    VyOS validates static-mapping names as *hostnames*, so underscores are
+    rejected outright -- verified: `Dongle-M_C0D4` fails with "Invalid static
+    mapping hostname". Letters, digits and hyphens only, no leading digit or
+    hyphen, no trailing hyphen.
+    """
+    cleaned = re.sub(r"[^A-Za-z0-9-]", "-", (name or "").strip())
+    cleaned = re.sub(r"-{2,}", "-", cleaned).strip("-")
+    if cleaned and cleaned[0].isdigit():
+        cleaned = "h" + cleaned
+    return cleaned or fallback
+
+
+class Mapper:
+    """Translates production addresses into the target mode's address space.
+
+    In prod mode this is the identity. In sim mode an address is mapped by its
+    offset from the network address, so the host part is preserved: 10.0.0.46
+    -> 172.31.10.46 and 10.0.1.67 -> 172.31.11.67. That is what makes the sim
+    test meaningful -- the MAC is identical and the host octet is recognisable.
+    """
+
+    def __init__(self, mode: str, networks: list) -> None:
+        self.mode = mode
+        self.clamped: list[str] = []
+        self.map: dict[int, tuple] = {}
+        for n in networks:
+            prod = ipaddress.ip_network(
+                ipaddress.ip_interface(n["subnet"]).network)
+            if mode == "sim":
+                sim = ipaddress.ip_network(SIM_SUBNETS[vlan_of(n)])
+            else:
+                sim = prod
+            self.map[vlan_of(n)] = (prod, sim)
+
+    def net(self, vlan: int) -> ipaddress.IPv4Network:
+        return self.map[vlan][1]
+
+    def addr(self, vlan: int, ip: str, what: str) -> str | None:
+        """Map one address, or None if it does not fit the target subnet."""
+        prod, sim = self.map[vlan]
+        offset = int(ipaddress.ip_address(ip)) - int(prod.network_address)
+        if offset < 0 or offset >= sim.num_addresses:
+            self.clamped.append(f"{what}: {ip} does not fit {sim}")
+            return None
+        return str(ipaddress.ip_address(int(sim.network_address) + offset))
+
+    def gateway(self, vlan: int, net: dict) -> str:
+        """The address clients are told to use as their default route.
+
+        Production: the USG's current address (VIPs move .254 -> .1 at cutover),
+        so no client has to change anything. Sim: the sim router at .1.
+        """
+        if self.mode == "sim":
+            return str(self.net(vlan).network_address + 1)
+        return str(ipaddress.ip_interface(net["subnet"]).ip)
+
+
+def build(inv: dict, mode: str) -> tuple[list[str], dict]:
+    nets = [n for n in inv["networks"] if n["dhcp_enabled"] and n["subnet"]]
+    nets.sort(key=vlan_of)
+    m = Mapper(mode, nets)
+
+    out: list[str] = []
+    used_tags: set[str] = set()
+    stats = {"subnets": 0, "mappings": 0, "dropped": []}
+    by_vlan: dict[int, list] = {}
+    for r in inv["reservations"]:
+        if r["network_vlan"] is None and r["network_name"] != "Management":
+            # resolved_by == "unresolved"; cannot place it without a subnet
+            stats["dropped"].append(f"{r['ip']} {r['mac']} (no network)")
+            continue
+        by_vlan.setdefault(r["network_vlan"] or 1, []).append(r)
+
+    out.append("# --- DHCP ---------------------------------------------------")
+    for n in nets:
+        vlan = vlan_of(n)
+        sub = m.net(vlan)
+        base = f"set service dhcp-server shared-network-name {sanitize(n['name'], f'vlan{vlan}')} subnet {sub}"
+        gw = m.gateway(vlan, n)
+
+        out.append("")
+        out.append(f"# {n['name']} (VLAN {vlan}) <- {n['subnet']}")
+        # subnet-id is required by kea and must be stable across regenerations;
+        # the VLAN id is already the unique per-network number in this lab.
+        out.append(f"{base} subnet-id {vlan}")
+        out.append(f"{base} option default-router {gw}")
+
+        # Every VLAN is handed the gateway as its resolver, so all lookups go
+        # through VyOS and out to the upstreams above. UniFi set an explicit
+        # resolver on LoT only (the NAS); that is deliberately not carried over
+        # -- the NAS is legacy and pointing clients at it would keep it in the
+        # path for one VLAN and not the others.
+        out.append(f"{base} option name-server {gw}")
+
+        if n["domain_name"]:
+            out.append(f"{base} option domain-name '{n['domain_name']}'")
+        if n["dhcp_lease"]:
+            out.append(f"{base} lease {n['dhcp_lease']}")
+
+        start = m.addr(vlan, n["dhcp_start"], f"{n['name']} range start")
+        stop = m.addr(vlan, n["dhcp_stop"], f"{n['name']} range stop")
+        if start is None:
+            start = str(sub.network_address + 11)
+        if stop is None:
+            # Clamp to the last usable address rather than dropping the pool.
+            stop = str(sub.broadcast_address - 1)
+        out.append(f"{base} range LAN start {start}")
+        out.append(f"{base} range LAN stop {stop}")
+        stats["subnets"] += 1
+
+        for r in sorted(by_vlan.get(vlan, []), key=lambda x: ipaddress.ip_address(x["ip"])):
+            ip = m.addr(vlan, r["ip"], f"reservation {r['name']}")
+            if ip is None:
+                stats["dropped"].append(f"{r['ip']} {r['mac']} ({r['name']})")
+                continue
+            tag = sanitize(r["name"] or r["hostname"], "host-" + r["mac"].replace(":", ""))
+            # Distinct clients can sanitize to the same name; a collision would
+            # silently overwrite one reservation with another's address.
+            if tag in used_tags:
+                tag = f"{tag}-{r['mac'].replace(':', '')[-4:]}"
+            used_tags.add(tag)
+            out.append(f"{base} static-mapping {tag} mac {r['mac']}")
+            out.append(f"{base} static-mapping {tag} ip-address {ip}")
+            stats["mappings"] += 1
+
+    out.append("")
+    out.append("# --- DNS ----------------------------------------------------")
+    out.append("# The USG resolves for 5 of 6 VLANs today (it hands out its own")
+    out.append("# address when dhcpd_dns is empty). Without this, they lose DNS.")
+    for n in nets:
+        vlan = vlan_of(n)
+        out.append(f"set service dns forwarding listen-address {m.gateway(vlan, n)}")
+        out.append(f"set service dns forwarding allow-from {m.net(vlan)}")
+    for ns in UPSTREAM_DNS:
+        out.append(f"set service dns forwarding name-server {ns}")
+    out.append("set service dns forwarding cache-size 10000")
+
+    stats["clamped"] = m.clamped
+    return out, stats
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser()
+    here = os.path.dirname(os.path.abspath(__file__))
+    ap.add_argument("--mode", choices=("prod", "sim"), required=True)
+    ap.add_argument("--inventory", default=os.path.join(here, "export", "inventory.json"))
+    ap.add_argument("-o", "--out")
+    ap.add_argument("--check", action="store_true", help="counts only, no config")
+    args = ap.parse_args()
+
+    with open(args.inventory) as fh:
+        inv = json.load(fh)
+
+    lines, stats = build(inv, args.mode)
+
+    expected = len(inv["reservations"])
+    print(f"mode={args.mode}  subnets={stats['subnets']}  "
+          f"static-mappings={stats['mappings']}/{expected}", file=sys.stderr)
+    for c in stats["clamped"]:
+        print(f"  clamped: {c}", file=sys.stderr)
+    for d in stats["dropped"]:
+        print(f"  DROPPED: {d}", file=sys.stderr)
+
+    if stats["mappings"] != expected and args.mode == "prod":
+        print(f"ERROR: {expected - stats['mappings']} reservation(s) missing from "
+              f"prod output -- every one must survive the cutover", file=sys.stderr)
+        return 1
+
+    if args.check:
+        return 0
+
+    text = "\n".join(lines) + "\n"
+    if args.out:
+        with open(args.out, "w") as fh:
+            fh.write(text)
+        print(f"wrote {args.out}", file=sys.stderr)
+    else:
+        sys.stdout.write(text)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())

migration/vif53-pin-boot-disable

@@ -0,0 +1,111 @@
+#!/bin/sh
+# Make config.boot carry `vif 53 disable` while the RUNNING config keeps the
+# 10 gig up. Run on the master. Idempotent.
+#
+# WHY THIS IS AWKWARD
+#
+# The convention is that BOTH routers' config.boot hold `vif 53 disable`, so a
+# reboot in any order comes up unable to claim the cloned MAC
+# (f0:9f:c2:12:9b:4f) and vrrp-wan-reconcile then enables it on whichever box
+# holds the VIP. The master's RUNNING config must have it enabled -- it is
+# carrying the WAN -- so config.boot and the running config must deliberately
+# disagree.
+#
+# VyOS gives no clean way to express that. `save` writes the RUNNING config,
+# not the candidate: setting the node, saving, then discarding was tested in
+# labsim and config.boot came back without `disable`, the WAN untouched. So the
+# only route is to genuinely disable it, save that, and re-enable -- a real,
+# brief interruption of the 10 gig.
+#
+# WHAT THE INTERRUPTION ACTUALLY COSTS
+#
+# Not the internet, on a healthy pair: pppoe0 is up on the master and the
+# failover route falls to it while bond0.53 is down, which is exactly the
+# behaviour T5 proves in labsim (LAN back in 5s). Traffic moves to the slower
+# line and back. Expect a few seconds, plus however long the ISP takes to
+# re-issue the DHCP lease afterwards.
+#
+# IF THIS SCRIPT DIES HALFWAY it leaves the master with bond0.53 disabled --
+# which vrrp-wan-reconcile repairs within 30s ("MASTER with bond0.53 disabled
+# -> enabling"). The failure mode is bounded by design, not by luck.
+#
+#     sudo /config/vif53-pin-boot-disable          do it
+#     sudo /config/vif53-pin-boot-disable --check  report only, change nothing
+
+VIF=53
+BOOT=/config/config.boot
+
+cfg() { /opt/vyatta/bin/vyatta-op-cmd-wrapper show configuration commands 2>/dev/null; }
+boot_has() { awk "/vif ${VIF} {/,/^        }/" "$BOOT" 2>/dev/null | grep -qc disable 2>/dev/null; }
+boot_disable_count() { awk "/vif ${VIF} {/,/^        }/" "$BOOT" 2>/dev/null | grep -c disable; }
+run_disable_count() { cfg | grep -c "vif ${VIF} disable"; }
+
+report() {
+    printf '  running config disable : %s\n' "$(run_disable_count)"
+    printf '  config.boot   disable : %s\n' "$(boot_disable_count)"
+    printf '  bond0.%s address      : %s\n' "$VIF" \
+        "$(ip -4 addr show "bond0.${VIF}" 2>/dev/null | sed -n 's/.*inet \([0-9.]*\).*/\1/p')"
+}
+
+if [ "${1:-}" = "--check" ]; then report; exit 0; fi
+
+if [ "$(boot_disable_count)" -ge 1 ]; then
+    echo "  config.boot already pins 'vif ${VIF} disable' -- nothing to do"
+    report
+    exit 0
+fi
+
+# Refuse on a box that is not carrying the WAN: there the running config should
+# already have `disable`, and a plain `save` is all that is needed. Doing the
+# dance here would be pointless downtime.
+if [ "$(run_disable_count)" -ge 1 ]; then
+    echo "  this box already has 'vif ${VIF} disable' in the running config;"
+    echo "  a plain 'save' is enough and costs nothing. Not touching the WAN."
+    exit 0
+fi
+
+# Serialise against vrrp-wan-reconcile by taking ITS lock. Without this the two
+# commit at the same time and VyOS refuses one of them with "Configuration
+# system temporarily locked due to another commit in progress" -- observed in
+# labsim, where the `save` landed but the RE-ENABLE did not, leaving the master
+# with its 10 gig down. The reconciler uses `flock -n` and simply skips a tick
+# it cannot get, so holding this is cheap and safe.
+exec 9>/run/vrrp-wan.lock
+if ! flock -w 60 9; then
+    echo "  could not take /run/vrrp-wan.lock within 60s -- is a commit stuck?"
+    echo "  refusing to race vrrp-wan-reconcile for the config lock."
+    exit 1
+fi
+
+logger -t vif53-pin "pinning 'vif ${VIF} disable' into config.boot -- bond0.${VIF} will bounce"
+echo "  bouncing bond0.${VIF} to get 'disable' into config.boot..."
+t0=$(date +%s)
+
+# 9>&- so the config session's long-lived unionfs-fuse child does not inherit
+# the lock fd and hold it for ever -- the same trap vrrp-wan-reconcile documents.
+/bin/vbash 9>&- <<VBASH
+source /opt/vyatta/etc/functions/script-template
+configure
+set interfaces bonding bond0 vif ${VIF} disable
+commit
+save
+delete interfaces bonding bond0 vif ${VIF} disable
+commit
+exit
+VBASH
+rc=$?
+
+echo "  window: $(( $(date +%s) - t0 ))s (exit $rc)"
+logger -t vif53-pin "done in $(( $(date +%s) - t0 ))s"
+report
+
+# Belt and braces: if the re-enable did not take, say so loudly. The reconciler
+# will fix it within 30s on a master, but silence here would look like success.
+if [ "$(run_disable_count)" -ge 1 ]; then
+    echo "  *** WARNING: bond0.${VIF} is STILL disabled in the running config."
+    echo "  *** vrrp-wan-reconcile should re-enable it within 30s on the master."
+    echo "  *** Force it now with: sudo /config/vrrp-wan-reconcile"
+    exit 1
+fi
+[ "$(boot_disable_count)" -ge 1 ] || { echo "  *** config.boot still not pinned"; exit 1; }
+echo "  OK: config.boot pinned, running config still has the WAN"

migration/vlan2-v6-apply

@@ -0,0 +1,189 @@
+#!/bin/bash
+# Give VLAN 2 (the k8s VLAN) IPv6: addresses, router advertisements and DHCPv6
+# reservations. Production half of dual-stack phase 2b.
+#
+# Rehearsed first as labsim/labsim-dualstack-net.sh, which is where the four
+# VyOS facts below were paid for rather than guessed.
+#
+# ADDRESSING ONLY -- NOT EGRESS. The prefix is advertised with
+# `default-lifetime 0`, so nodes get their reserved addresses but neither router
+# becomes an IPv6 default router. Turning on real v6 egress moves cluster image
+# pulls onto the HE tunnel (1480, or 1472 on PPPoE) whose throughput has never
+# been measured, and that is not a thing to switch on unattended. Flipping it is
+# one line: `set service router-advert interface bond0.2 default-lifetime '1800'`
+# plus a default-preference, once somebody is watching.
+#
+# LISTEN-INTERFACE IS NOT OPTIONAL. Without it kea6 renders
+# `interfaces: [ "*" ]` and serves DHCPv6 on EVERY VLAN, not just this one.
+# Observed in production the moment this was first applied: kea started
+# answering SOLICIT/REQUEST from an unrelated device on bond0.10 (LoT). That is
+# a DHCPv6 server switched on estate-wide as a side effect of configuring one
+# VLAN -- the same family of mistake as the kea IPv4 cross-VLAN bug (ISC #1117)
+# this estate already fought. Pin the interface.
+#
+# WHY DHCPv6 RATHER THAN SLAAC: k3s resolves node-ip once at start-up, so a
+# node's address must be knowable in advance and stable. The estate already
+# answers that for IPv4 with kea reservations keyed on MAC; IPv6 answers it the
+# same way, from the same MACs, so there is one source of truth. VyOS's
+# static-mapping accepts `mac` as well as `duid`, which is what makes that
+# possible -- DHCPv6 normally keys on a client-generated DUID.
+#
+#   vlan2-v6-apply plan     print what would be applied, change nothing
+#   vlan2-v6-apply apply    apply to both routers
+#   vlan2-v6-apply verify   what the routers and nodes now hold
+#   vlan2-v6-apply revert   remove it again
+set -uo pipefail
+
+R1="${R1:-10.0.1.252}"   # vyos001 -> ::1
+R2="${R2:-10.0.1.253}"   # vyos002 -> ::2
+PW="${VYOS_PW:-vyos}"
+V6_PREFIX="${V6_PREFIX:-2001:470:187e:2}"
+LINK_MTU="${LINK_MTU:-1472}"
+SUBNET_ID="${SUBNET_ID:-2}"          # VyOS requires a unique id per DHCPv6 subnet
+SHARED_NET="${SHARED_NET:-TheLab-k8s}"
+
+# name:v4-host-octet -- the IPv6 host part mirrors the IPv4 one so a reservation
+# is readable next to its twin. MACs are read from the LIVE IPv4 reservations at
+# run time, never duplicated here: one source of truth, and a node that is
+# re-homed cannot end up with a stale v6 mapping.
+NODES=(worker0-k8s0:23 worker1-k8s0:13 worker2-k8s0:25 spark-2935:12 aitopatom-3a1c:27)
+
+SSH=(-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null
+     -o LogLevel=ERROR -o ConnectTimeout=8)
+
+# stderr, NOT stdout. build_mappings() is captured with $(...) and log() lines
+# went straight into the config stream, where VyOS rejected each one as
+# "Invalid command: [[0" -- ANSI escapes and all. The valid sets still applied,
+# so the routers ended up correct but NOT identical: different lines were lost
+# on each. A progress message is not data; keep it off the data channel.
+log()  { printf '\033[0;36m[vlan2-v6]\033[0m %s\n' "$*" >&2; }
+die()  { printf '\033[0;31m[vlan2-v6]\033[0m %s\n' "$*" >&2; exit 1; }
+
+r() { timeout 45 ssh "${SSH[@]}" "vyos@$1" "${@:2}" 2>/dev/null; }
+
+# Drive VyOS from a script FILE with plain commit + save.
+#   - `vbash -c` never starts a config session; the commit fails to stderr and a
+#     helper discards it, so the run reports success having changed nothing.
+#   - `commit-confirm` hangs non-interactively and strands an orphaned
+#     config-mgmt commit_confirm holding the config lock.
+#   - vbash exits 0 even when the commit fails, so the OUTPUT is the only honest
+#     signal. Read it.
+vyos_apply() {
+    local h="$1" out
+    out="$({ printf '#!/bin/vbash\nsource /opt/vyatta/etc/functions/script-template\nconfigure\n'
+             cat
+             printf 'commit\nsave\nexit\n'
+           } | timeout 150 ssh "${SSH[@]}" "vyos@$h" \
+                 'cat > /tmp/vlan2-v6.sh && chmod +x /tmp/vlan2-v6.sh && sudo /tmp/vlan2-v6.sh' 2>&1)"
+    printf '%s\n' "$out" | grep -vE '^\s*$' | sed 's/^/      /' | tail -8
+    # "Invalid command" was NOT in this list the first time, so a run that fed
+    # rubbish to VyOS reported success. vbash exits 0 regardless, so every
+    # rejection shape has to be named explicitly.
+    printf '%s' "$out" | grep -qiE 'Commit failed|\[\[.*\]\] failed|Set failed|Invalid command' && return 1
+    return 0
+}
+
+# Read each node's MAC out of the live IPv4 reservation.
+#
+# Scoped to the IPv4 subnet on purpose. Once this script has run once, the node
+# has TWO `static-mapping <name> mac` lines -- the v4 one and the v6 one it just
+# created -- and an unscoped match returned both concatenated
+# ("9c:76:0e:49:e9:179c:76:0e:49:e9:17"), which VyOS then rejected as an invalid
+# value. Self-inflicted on the second run: the lookup has to name the subnet it
+# means, or the script poisons its own input as soon as it succeeds.
+V4_SUBNET="${V4_SUBNET:-192.168.8.0/23}"
+mac_of() {
+    r "$R1" "/opt/vyatta/bin/vyatta-op-cmd-wrapper show configuration commands 2>/dev/null \
+        | grep -F 'subnet $V4_SUBNET' \
+        | sed -n \"s/.*static-mapping $1 mac '\\(.*\\)'/\\1/p\"" | tr -d ' \n'
+}
+
+build_mappings() {
+    local out="" name hextet mac
+    for entry in "${NODES[@]}"; do
+        name="${entry%%:*}"; hextet="${entry##*:}"
+        mac="$(mac_of "$name")"
+        [ -n "$mac" ] || die "no IPv4 reservation found for $name -- refusing to invent a MAC"
+        log "    $name  $mac  -> ${V6_PREFIX}::${hextet}"
+        [ -n "$out" ] && out+=$'\n'
+        out+="set service dhcpv6-server shared-network-name ${SHARED_NET} subnet ${V6_PREFIX}::/64 static-mapping ${name} mac '${mac}'
+set service dhcpv6-server shared-network-name ${SHARED_NET} subnet ${V6_PREFIX}::/64 static-mapping ${name} ipv6-address '${V6_PREFIX}::${hextet}'"
+    done
+    printf '%s' "$out"
+}
+
+# One commit per router, and `no-autonomous-flag` is in it. That is not a
+# style choice: turning autonomous off LATER does not retract addresses already
+# formed, so a prefix advertised even briefly without it leaves every node
+# holding an unreserved EUI-64 address with a 30-day lifetime. Observed in the
+# sim. VLAN 2 has no IPv6 today, so this is the one chance to get it right.
+config_for() {
+    local self="$1" mappings="$2"
+    cat <<EOF
+set interfaces bonding bond0 vif 2 address '${V6_PREFIX}::${self}/64'
+set service router-advert interface bond0.2 prefix ${V6_PREFIX}::/64 no-autonomous-flag
+set service router-advert interface bond0.2 prefix ${V6_PREFIX}::/64 valid-lifetime '2592000'
+set service router-advert interface bond0.2 prefix ${V6_PREFIX}::/64 preferred-lifetime '604800'
+set service router-advert interface bond0.2 managed-flag
+set service router-advert interface bond0.2 link-mtu '${LINK_MTU}'
+set service router-advert interface bond0.2 default-lifetime '0'
+set service dhcpv6-server listen-interface bond0.2
+set service dhcpv6-server shared-network-name ${SHARED_NET} subnet ${V6_PREFIX}::/64 subnet-id '${SUBNET_ID}'
+set service dhcpv6-server shared-network-name ${SHARED_NET} subnet ${V6_PREFIX}::/64 interface 'bond0.2'
+${mappings}
+EOF
+}
+
+cmd_plan() {
+    log "reading MACs from the live IPv4 reservations"
+    local m; m="$(build_mappings)" || exit 1
+    echo; log "--- vyos001 (${V6_PREFIX}::1) ---"; config_for 1 "$m" | sed 's/^/  /'
+    echo; log "--- vyos002 (${V6_PREFIX}::2) ---"; config_for 2 "$m" | sed 's/^/  /'
+}
+
+cmd_apply() {
+    log "reading MACs from the live IPv4 reservations"
+    local m; m="$(build_mappings)" || exit 1
+    local h self
+    for h in "$R1" "$R2"; do
+        [ "$h" = "$R1" ] && self=1 || self=2
+        log "applying to $h (${V6_PREFIX}::${self})"
+        config_for "$self" "$m" | vyos_apply "$h" \
+            || die "commit failed on $h -- NOTE: VyOS commits node groups independently, so re-read the config rather than assuming rollback"
+    done
+    log "applied. Nodes should take their reservations within a few minutes."
+}
+
+cmd_verify() {
+    local h
+    for h in "$R1" "$R2"; do
+        printf '  --- %s ---\n' "$h"
+        printf '    bond0.2 v6 : %s\n' "$(r "$h" 'ip -6 -br addr show bond0.2 | tr -s " "')"
+        printf '    radvd      : %s (inactive on the backup is CORRECT)\n' "$(r "$h" 'systemctl is-active radvd')"
+        printf '    kea-dhcp6  : %s\n' "$(r "$h" 'c=$(ps -ef | grep -c "[k]ea-dhcp6"); [ "$c" -gt 0 ] && echo running || echo "NOT running"')"
+        printf '    role       : %s\n' "$(r "$h" 'sudo /config/vrrp-wan-reconcile --status 2>/dev/null | grep -o "role=[a-z]*"')"
+        printf '    IPv4 sane  : %s\n' "$(r "$h" 'ip -4 route show default | head -1')"
+    done
+}
+
+cmd_revert() {
+    local h self
+    for h in "$R1" "$R2"; do
+        [ "$h" = "$R1" ] && self=1 || self=2
+        log "reverting $h"
+        vyos_apply "$h" <<EOF
+delete service dhcpv6-server
+delete service router-advert interface bond0.2
+delete interfaces bonding bond0 vif 2 address '${V6_PREFIX}::${self}/64'
+EOF
+    done
+    log "reverted"
+}
+
+case "${1:-plan}" in
+    plan)   cmd_plan ;;
+    apply)  cmd_apply ;;
+    verify) cmd_verify ;;
+    revert) cmd_revert ;;
+    *) die "usage: $0 {plan|apply|verify|revert}" ;;
+esac

migration/vlan2-v6-watchdog

@@ -0,0 +1,133 @@
+#!/bin/bash
+# Auto-revert the VLAN 2 IPv6 change if IPv4 stops working.
+#
+# The change it guards is additive and IPv6-only, so in theory it cannot affect
+# IPv4 at all. This exists because "in theory" is exactly what has been wrong
+# repeatedly, and because it is applied in an unattended window: the person who
+# would notice is away, and a router that has lost IPv4 takes the house and the
+# cluster with it.
+#
+# Modelled on wan-drill-watchdog: arm before the risky thing, disarm after, and
+# in between let the ROUTER decide for itself rather than depending on anything
+# off-box. A watchdog that needs the network it is protecting is not a watchdog.
+#
+#   vlan2-v6-watchdog arm [seconds]   start watching (default 2400 = 40 min)
+#   vlan2-v6-watchdog disarm          stop
+#   vlan2-v6-watchdog status          is it armed, and what has it seen
+#
+# Runs ON the router, out of /config, detached via setsid so it outlives the ssh
+# session that started it.
+set -uo pipefail
+
+STATE=/run/vlan2-v6-watchdog
+PIDF=$STATE/pid
+LOGF=$STATE/log
+V6_PREFIX="${V6_PREFIX:-2001:470:187e:2}"
+
+# How long IPv4 must be continuously bad before reverting. Long enough that a
+# commit's own brief disruption, or one lost probe, does not trigger it; short
+# enough to matter. The reconciler ticks at 30s, so 90s is three chances.
+GRACE="${GRACE:-90}"
+PROBE="${PROBE:-9.9.9.9}"
+
+log() { mkdir -p "$STATE"; printf '%s %s\n' "$(date -Is)" "$*" >> "$LOGF"; }
+
+# IPv4 health, asked of the box itself -- and it MUST be role-aware.
+#
+# The first version required a default route plus internet on both routers, and
+# would have reverted on vyos002 within 90s of being armed. That box is the
+# gated BACKUP: by design it holds no VIP, has bond0.53 disabled and pppoe0
+# down, so it has no default route and no internet, and that is the correct
+# resting state rather than a fault. Caught at 20s of the 90s grace.
+#
+# So: the master must be able to reach the internet. The backup only has to
+# still be on the network and able to see its peer -- which is what would
+# actually be at risk if a VLAN 2 change went wrong.
+VIP="${VIP:-192.168.1.1}"
+holds_vip() { ip -4 -o addr show 2>/dev/null | grep -q " ${VIP}/"; }
+
+v4_ok() {
+    if holds_vip; then
+        ip -4 route show default 2>/dev/null | grep -q . || return 1
+        ping -c1 -W2 "$PROBE" >/dev/null 2>&1
+    else
+        # Backup: management address present and the VIP answers. If the VIP has
+        # gone too then the pair has a bigger problem than this change, and
+        # reverting an IPv6 addition would not help -- so this deliberately does
+        # not fire on peer loss alone.
+        ip -4 -o addr show bond0.1 2>/dev/null | grep -q 'inet ' || return 1
+        ping -c1 -W2 "$VIP" >/dev/null 2>&1
+    fi
+}
+
+revert() {
+    log "REVERTING: IPv4 has been down for ${GRACE}s"
+    # A script file, not vbash -c: the latter never starts a config session and
+    # the commit fails to stderr where nobody sees it.
+    cat > /tmp/vlan2-v6-revert.sh <<'REOF'
+#!/bin/vbash
+source /opt/vyatta/etc/functions/script-template
+configure
+delete service dhcpv6-server
+delete service router-advert interface bond0.2
+commit
+save
+exit
+REOF
+    chmod +x /tmp/vlan2-v6-revert.sh
+    /tmp/vlan2-v6-revert.sh >> "$LOGF" 2>&1
+    # The interface address is deleted separately: it is the one node whose
+    # removal could plausibly disturb something else, so it goes last and its
+    # failure does not block the rest.
+    for n in 1 2; do
+        ip -6 addr del "${V6_PREFIX}::${n}/64" dev bond0.2 2>/dev/null
+    done
+    log "revert done; IPv4 now $(v4_ok && echo OK || echo STILL BAD)"
+}
+
+watch_loop() {
+    local deadline=$(( $(date +%s) + $1 )) bad=0
+    log "armed for $1s (grace ${GRACE}s, probe ${PROBE})"
+    while [ "$(date +%s)" -lt "$deadline" ]; do
+        if v4_ok; then
+            [ "$bad" -ne 0 ] && log "IPv4 recovered after ${bad}s"
+            bad=0
+        else
+            bad=$((bad + 10))
+            log "IPv4 bad (${bad}s/${GRACE}s)"
+            if [ "$bad" -ge "$GRACE" ]; then
+                revert
+                log "disarming after revert"
+                rm -f "$PIDF"
+                return 0
+            fi
+        fi
+        sleep 10
+    done
+    log "expired without incident"
+    rm -f "$PIDF"
+}
+
+case "${1:-status}" in
+    arm)
+        mkdir -p "$STATE"
+        [ -f "$PIDF" ] && kill -0 "$(cat "$PIDF")" 2>/dev/null && { echo "already armed"; exit 0; }
+        setsid "$0" _run "${2:-2400}" >/dev/null 2>&1 < /dev/null &
+        sleep 1
+        [ -f "$PIDF" ] && echo "  armed (pid $(cat "$PIDF"), ${2:-2400}s)" || echo "  FAILED to arm"
+        ;;
+    _run)
+        echo $$ > "$PIDF"
+        watch_loop "${2:-2400}"
+        ;;
+    disarm)
+        if [ -f "$PIDF" ]; then kill "$(cat "$PIDF")" 2>/dev/null; rm -f "$PIDF"; echo "  disarmed"
+        else echo "  not armed"; fi
+        ;;
+    status)
+        if [ -f "$PIDF" ] && kill -0 "$(cat "$PIDF")" 2>/dev/null; then echo "  armed (pid $(cat "$PIDF"))"
+        else echo "  not armed"; fi
+        echo "  --- log ---"; tail -12 "$LOGF" 2>/dev/null | sed 's/^/  /' || echo "  (none)"
+        ;;
+    *) echo "usage: $0 {arm [seconds]|disarm|status}" >&2; exit 2 ;;
+esac

migration/vrrp-wan-apply

@@ -0,0 +1,52 @@
+#!/bin/vbash
+# Enable or disable the DHCP WAN (bond0.53). The ONLY part of the failover that
+# touches VyOS configuration.
+#
+# PPPoE deliberately does NOT appear here any more, and should not be added back
+# for symmetry. `set interfaces pppoe pppoe0 disable` unlinks
+# /etc/ppp/peers/pppoe0 -- interfaces_pppoe.py treats `disable` and `delete`
+# identically -- and that path is pppd's options file, so the resting state
+# destroyed what the promotion path needed and the unit restart-looped (47 times,
+# zero sessions at the AC). It also made a pppoe node able to fail this commit
+# and take the 10 gig down with it: `interfaces pppoe` is priority 322 and one
+# invalid node fails the whole commit. PPPoE is now gated at the systemd unit
+# instead; see migration/ppp-vrrp-gate.conf and vrrp-wan-reconcile.
+#
+# bond0.53 stays here because its lease is bound to a cloned MAC and only VyOS
+# config can move a MAC between boxes.
+#
+# `source /opt/vyatta/etc/functions/script-template` must be the FIRST thing the
+# script does. Sourced after an if, an exec and a mkdir it terminated the script
+# inside the source, rc=0, no output -- the caller reported success having done
+# nothing. Only a single assignment may precede it (the template resets the
+# positional parameters), which is the shape /config/vyos-known-good uses.
+#
+#   vrrp-wan-apply enable    take the DHCP WAN
+#   vrrp-wan-apply disable   release it
+MODE="${1:-}"
+source /opt/vyatta/etc/functions/script-template
+
+CONF=/config/vrrp-wan.conf
+[ -r "$CONF" ] && . "$CONF"
+WAN_VIF="${WAN_VIF:-53}"
+
+cfg() { /opt/vyatta/bin/vyatta-op-cmd-wrapper show configuration commands 2>/dev/null; }
+wan_disabled(){ cfg | grep -q "vif ${WAN_VIF} disable"; }
+
+configure
+if [ "$MODE" = enable ]; then
+    # Guarded: `delete` of an absent node aborts the whole batch with
+    # "Nothing to delete", which once left the box detected-but-unfixed.
+    wan_disabled && delete interfaces bonding bond0 vif ${WAN_VIF} disable
+else
+    wan_disabled || set interfaces bonding bond0 vif ${WAN_VIF} disable
+fi
+# Report the commit's verdict. This script previously ended on `exit` (a
+# script-template function) and returned 0 even after "Commit failed", so the
+# reconciler logged a release that had not happened -- the worst kind of failure
+# for something whose job is to keep two routers from holding one WAN.
+if commit 2>&1 | tee /tmp/vrrp-wan-commit.log | grep -qi "commit failed"; then
+    logger -t vrrp-wan "COMMIT FAILED applying '$MODE' -- see /tmp/vrrp-wan-commit.log"
+    exit 1
+fi
+exit

migration/vrrp-wan-guard

@@ -0,0 +1,45 @@
+#!/bin/sh
+# Revoke the PPPoE dial lease. Runs every 5s. Only ever takes the WAN AWAY.
+#
+# vrrp-wan-reconcile is the single writer and runs every 30s; this is the
+# watcher, and it exists because `may-dial` must be a LEASE, not a flag.
+# ConditionPathExists is evaluated at START only -- it can prevent a dial, it can
+# never revoke one. So if the reconciler stops running (timer masked, box wedged,
+# someone stops it during maintenance) and the box is then demoted, nothing would
+# ever hang up: it would keep the one ISP session while the new master tries to
+# take it.
+#
+# Two conditions revoke, both biased the safe way:
+#   - this box does not hold the management VIP
+#   - the lease has not been renewed within LEASE_TTL (the reconciler is dead)
+#
+# Deliberately tiny: no config mode, no flock, no commit. It cannot wedge the
+# router's configuration system, which is what earns it a 5s timer. Running at
+# 5s rather than the reconciler's 30s is also what shrinks the double-dial
+# window on a demotion from up to 30s down to about 5.
+
+CONF=/config/vrrp-wan.conf
+[ -r "$CONF" ] && . "$CONF"
+VIP="${VRRP_WAN_VIP:-192.168.1.1}"
+LEASE_TTL="${LEASE_TTL:-75}"
+STATE=/run/vrrp-wan
+
+revoke() {
+    rm -f "$STATE/may-dial"
+    systemctl is-active --quiet ppp@pppoe0 2>/dev/null || return 0
+    logger -t vrrp-wan "GUARD: $1 -- hanging up pppoe0"
+    systemctl stop ppp@pppoe0 2>/dev/null
+}
+
+if ! ip -4 -o addr show 2>/dev/null | grep -q " ${VIP}/"; then
+    revoke "does not hold ${VIP}"
+    exit 0
+fi
+
+# Holds the VIP, so it is entitled to dial -- but only while something is
+# actively renewing the lease on its behalf.
+if [ -f "$STATE/may-dial" ]; then
+    age=$(( $(date +%s) - $(stat -c %Y "$STATE/may-dial" 2>/dev/null || echo 0) ))
+    [ "$age" -gt "$LEASE_TTL" ] && revoke "lease stale (${age}s > ${LEASE_TTL}s; is vrrp-wan-reconcile.timer running?)"
+fi
+exit 0

migration/vrrp-wan-guard.service

@@ -0,0 +1,10 @@
+[Unit]
+# Revokes the PPPoE dial lease. Only ever takes the WAN away, never grants it,
+# which is what makes a 5s cadence safe: it touches no VyOS configuration and
+# cannot wedge the commit lock.
+Description=Revoke the PPPoE dial lease when this router is not master
+After=vyos-router.service
+
+[Service]
+Type=oneshot
+ExecStart=/config/vrrp-wan-guard

migration/vrrp-wan-guard.timer

@@ -0,0 +1,13 @@
+[Unit]
+Description=Revoke the PPPoE dial lease every 5s
+
+[Timer]
+# 5s, against the reconciler's 30s. A demotion must hang up fast -- the window
+# between "no longer master" and "stopped dialling" is the window in which two
+# routers can hold one ISP session.
+OnBootSec=10
+OnUnitActiveSec=5
+AccuracySec=1
+
+[Install]
+WantedBy=timers.target

migration/vrrp-wan-health

@@ -0,0 +1,148 @@
+#!/bin/sh
+# VRRP health check: may THIS router hold the floating IPs?
+#
+# It may only if it can actually carry the WAN. Without this, VRRP decides
+# mastership purely on whether the peer is still advertising -- so a router with
+# no WAN at all happily takes the VIPs and blackholes the entire LAN's internet
+# while looking perfectly healthy. That is not hypothetical: it is the outage of
+# 2026-09-02, reproduced in labsim.
+#
+# ---------------------------------------------------------------------------
+# The first version of this script asked one question: "do I have an address on
+# a WAN interface". That is correct for a pair where both routers hold WAN all
+# the time. Ours cannot: the 10 gig lease is bound to a cloned MAC and the
+# PPPoE line to a single credential, so the WAN follows mastership (see
+# vrrp-wan-take). Against that design the old check DEADLOCKS --
+#
+#     may I be master?  ->  only if I already have WAN
+#     do I have WAN?    ->  only if I am master
+#
+# -- and the backup sits in FAULT for ever. vyos002 sat exactly there, which
+# meant the pair could not fail over at all: the safety check had quietly
+# removed the redundancy it was protecting.
+#
+# So the question is now asked in the right order: enforce "must have WAN" only
+# on the router that is actually HOLDING the VIPs, and give a new master time to
+# bring the WAN up before judging it.
+# ---------------------------------------------------------------------------
+#
+# exit 0 = eligible for MASTER, non-zero = release and let the peer have it.
+
+CONF=/config/vrrp-wan.conf
+[ -r "$CONF" ] && . "$CONF"
+STATE=/run/vrrp-wan
+VIP="${VRRP_WAN_VIP:-192.168.1.1}"
+
+# Seconds a new master may go without any WAN. Sourced from vrrp-wan.conf; the
+# fallback is deliberately NOT the old 90. accel-ppp's dead-peer budget is
+# lcp-echo-interval(30) x lcp-echo-failure(3) = 90s, so a hard failover into an
+# access concentrator that does not replace the stale session lands exactly on
+# the boundary: the new master fails its own check, sheds the VIPs, and the peer
+# -- in the same position -- does likewise. Both end in FAULT, which is worse
+# than the outage this check exists to prevent.
+#
+# The fallback tracks vrrp-wan.conf, where the reasoning and the measurements
+# live. Short version: labsim T4 timed a destroyed master's takeover at 26s
+# (replace), 148s (deny) and 21s (disable); `deny` is the sizing case and 180
+# left only 32s over it. Keep the two in step -- keepalived runs this script
+# with no environment, so if vrrp-wan.conf is ever missing THIS number is the
+# one that decides mastership.
+GRACE="${GRACE:-300}"
+
+# A deliberate hand-over lever.
+#
+# There is no reliable way to MAKE this pair fail over on demand. VyOS offers
+# only `restart vrrp`, and neither that nor `systemctl restart keepalived` is
+# dependable: with advert_int 1 the peer declares the master dead after ~3.6s,
+# and a restart usually finishes inside that window. Measured in labsim -- the
+# same command moved mastership on one run and not on the next three. A
+# fail-back procedure you cannot trigger on purpose is not a procedure.
+#
+# Failing the health check IS the supported way to shed mastership: the sync
+# group goes FAULT, releases every VIP, and the peer takes over -- the same path
+# a genuine WAN loss takes, so the planned drill exercises the real mechanism
+# rather than a special case.
+#
+#   touch /run/vrrp-wan/force-fault    hand over within failure-count*interval
+#   rm    /run/vrrp-wan/force-fault    become eligible again (no-preempt keeps
+#                                      it BACKUP until the peer hands back)
+#
+# It lives in /run deliberately: a reboot clears it, so a forgotten drill cannot
+# leave a router permanently ineligible.
+[ -f /run/vrrp-wan/force-fault ] && exit 1
+
+# Am I holding the VIPs? Asked of REALITY -- is the management VIP actually on
+# this box -- and not of a /run marker.
+#
+# The marker was the first design and it is unsafe: it is written by the VRRP
+# transition script, and in labsim that script silently failed to run on a
+# promotion (VyOS's keepalived-fifo.py helper stopped delivering while
+# keepalived's own notifies kept working). The router then believed it was
+# backup, passed this check, and sat holding every VIP with no WAN -- the exact
+# outage this script exists to prevent, re-created by trusting the reporter
+# instead of the fact.
+if [ -z "$(ip -4 -o addr show 2>/dev/null | grep " ${VIP}/")" ]; then
+    # Clear the grace stamp on the way down, HERE, not only in the reconciler.
+    # The reconciler runs every 30s; this runs every 5s. A promotion that
+    # inherited a stamp from an earlier mastership scored grace = hours, failed
+    # immediately, and took the sync group to FAULT ~5s after passing -- with the
+    # peer already faulted, that left BOTH routers in FAULT and the LAN with no
+    # gateway. The stamp must belong to the CURRENT mastership or it is worse
+    # than useless.
+    rm -f "$STATE/since" 2>/dev/null
+    exit 0
+fi
+
+# Start the grace clock HERE, the moment mastership is first observed.
+#
+# It used to be stamped only by vrrp-wan-reconcile, which runs on a 30s timer --
+# so a freshly promoted master reached this check with no stamp, scored grace=0,
+# failed, and went FAULT before it had any chance to bring the WAN up. The peer
+# then found itself alone with no WAN either and did the same. Observed in
+# labsim: BOTH routers in FAULT, nobody holding the VIPs, the LAN with no
+# gateway at all. That is worse than the outage this script exists to prevent,
+# and it would have hit a REAL failover, not just a drill -- the health check
+# runs every 5s and the reconciler had not yet ticked.
+mkdir -p "$STATE" 2>/dev/null
+[ -f "$STATE/since" ] || date +%s > "$STATE/since"
+
+# Master with an address on a WAN interface: healthy.
+#
+# Deliberately NOT "can I reach the internet" and NOT "do I have a default
+# route". During a real ISP outage the route disappears on BOTH routers; a check
+# keyed on that would put both into FAULT, nobody would hold the VIPs, and the
+# LAN would lose inter-VLAN routing too -- turning an internet outage into a
+# total one. A DHCP lease survives an ISP outage, so an address still
+# distinguishes "this box structurally cannot route" from "the internet is down
+# right now", which is the distinction that matters.
+# Any WAN counts. Requiring the 10 gig specifically would fault a healthy master
+# during a genuine 10 gig outage and turn a degraded state into a total one --
+# the same reasoning as the default-route note above. Which one satisfied it is
+# recorded for the operator and the test harness, but does not affect the verdict.
+for ifc in bond0.53 pppoe0; do
+    if ip -4 addr show dev "$ifc" 2>/dev/null | grep -q 'inet '; then
+        echo "$ifc" > "$STATE/wan" 2>/dev/null
+        # Re-stamp on every healthy tick, so the grace window below measures
+        # time since this box last DEMONSTRABLY had a WAN.
+        date +%s > "$STATE/since" 2>/dev/null
+        exit 0
+    fi
+done
+rm -f "$STATE/wan" 2>/dev/null
+
+# No WAN right now, but there was one within GRACE: ride it out.
+#
+# `since` is re-stamped on every healthy tick, so this measures time since the
+# box last HAD a WAN -- not time since it was promoted. Measuring from promotion
+# was wrong in a way that only shows up on an established master: after hours of
+# uptime `now - since` far exceeds any grace, so the first moment bond0.53 went
+# down and pppoe0 was mid-redial, the master failed its own check, shed every
+# VIP, and the peer -- inheriting the same WAN outage -- did the same. Observed
+# in labsim: taking the 10 gig down flapped the pair instead of falling back to
+# PPPoE. A WAN gap must be survivable wherever it happens, not only just after a
+# promotion.
+since=$(cat "$STATE/since" 2>/dev/null || echo 0)
+[ $(( $(date +%s) - since )) -lt "$GRACE" ] && exit 0
+
+# Master, past grace, still no WAN: release. This is the 2026-09-02 case.
+exit 1

migration/vrrp-wan-install

@@ -0,0 +1,115 @@
+#!/bin/bash
+# Install (or verify) the WAN-follows-VRRP mechanism on a VyOS router.
+#
+# This exists because on 2026-09-05 the sim's failover proof was obtained from
+# scripts that had been hand-`sed`-ed in place: /config/vrrp-wan-health and
+# -reconcile differed from git by an edited VIP, so the tested behaviour was not
+# the committed behaviour and any reinstall would have silently reverted it.
+# `--check` makes that class of drift a hard failure instead of a discovery.
+#
+# It installs ONLY the mechanism -- scripts, units, drop-in, settings. It never
+# touches VyOS configuration: the `interfaces pppoe` node, `vif 53 disable` and
+# the VRRP sync-group hooks are config and belong in the config model
+# (labsim/sim-*.py for the sim, infra/vyos/subtrees/overrides.json for
+# production), not in an installer.
+#
+#   vrrp-wan-install --vip 192.168.1.1 [--host vyos@10.0.1.253]
+#   vrrp-wan-install --check [--host ...]     # exits non-zero on any drift
+#
+# With no --host it operates on the local machine, so it can be scp'd to a
+# router and run there.
+set -uo pipefail
+
+HERE="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+VIP=""; HOST=""; MODE=install; PW="${VYOS_PW:-vyos}"
+
+while [ $# -gt 0 ]; do
+  case "$1" in
+    --vip)   VIP="$2"; shift 2 ;;
+    --host)  HOST="$2"; shift 2 ;;
+    --check) MODE=check; shift ;;
+    *) echo "usage: $0 [--vip A.B.C.D] [--host user@ip] [--check]" >&2; exit 2 ;;
+  esac
+done
+
+SSH_OPTS=(-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null
+          -o LogLevel=ERROR -o ConnectTimeout=8 -o PreferredAuthentications=password)
+run() {  # run a command on the target
+  if [ -n "$HOST" ]; then timeout 60 sshpass -p "$PW" ssh "${SSH_OPTS[@]}" "$HOST" "$@"
+  else bash -c "$*"; fi
+}
+put() {  # copy a file to the target
+  if [ -n "$HOST" ]; then timeout 60 sshpass -p "$PW" scp "${SSH_OPTS[@]}" "$1" "$HOST:$2" >/dev/null
+  else cp "$1" "$2"; fi
+}
+
+# script -> destination. take/release are hooks keepalived calls; both exec the
+# reconciler, so there is one code path.
+#
+# he-tunnel-follow is part of the mechanism, not a separate thing: the reconciler
+# owns tun0's link state and that script owns its source address and MTU. Listing
+# it here is what makes `--check` catch drift on it and what makes the VyOS
+# image-upgrade runbook reinstall it -- IPv6 was previously the one half of the
+# WAN story that no installer knew about.
+SCRIPTS="vrrp-wan-reconcile vrrp-wan-apply vrrp-wan-health vrrp-wan-guard vrrp-wan-take vrrp-wan-release he-tunnel-follow"
+UNITS="vrrp-wan-reconcile.service vrrp-wan-reconcile.timer vrrp-wan-guard.service vrrp-wan-guard.timer"
+GATE_DIR=/etc/systemd/system/ppp@pppoe0.service.d
+GATE=$GATE_DIR/10-vrrp-wan-gate.conf
+
+if [ "$MODE" = check ]; then
+  rc=0
+  for f in $SCRIPTS; do
+    local_sum=$(md5sum "$HERE/$f" | cut -d' ' -f1)
+    remote_sum=$(run "md5sum /config/$f 2>/dev/null | cut -d' ' -f1")
+    [ "$local_sum" = "$remote_sum" ] || { echo "  DRIFT /config/$f"; rc=1; }
+  done
+  for f in $UNITS; do
+    local_sum=$(md5sum "$HERE/$f" | cut -d' ' -f1)
+    remote_sum=$(run "md5sum /etc/systemd/system/$f 2>/dev/null | cut -d' ' -f1")
+    [ "$local_sum" = "$remote_sum" ] || { echo "  DRIFT /etc/systemd/system/$f"; rc=1; }
+  done
+  gate_sum=$(md5sum "$HERE/ppp-vrrp-gate.conf" | cut -d' ' -f1)
+  remote_gate=$(run "md5sum $GATE 2>/dev/null | cut -d' ' -f1")
+  [ "$gate_sum" = "$remote_gate" ] || { echo "  DRIFT $GATE (a VyOS upgrade wipes /etc -- both routers would dial)"; rc=1; }
+  run "[ -r /config/vrrp-wan.conf ]" || { echo "  MISSING /config/vrrp-wan.conf"; rc=1; }
+  # Secrets are placed by Pulumi (infra/vyos/secretsFile.ts), never by this
+  # installer, so check presence only -- there is no correct content to compare
+  # against and printing a diff of credentials would be worse than useless.
+  # Without it he-tunnel-follow cannot re-point the tunnel when the WAN falls
+  # back to PPPoE, which fails silently: IPv4 keeps working and IPv6 goes dark.
+  run "[ -r /config/he-secrets ]" || { echo "  MISSING /config/he-secrets (IPv6 cannot follow a WAN change)"; rc=1; }
+  for t in vrrp-wan-reconcile.timer vrrp-wan-guard.timer; do
+    [ "$(run "systemctl is-enabled $t 2>/dev/null")" = enabled ] || { echo "  NOT ENABLED $t"; rc=1; }
+  done
+  [ "$rc" -eq 0 ] && echo "  vrrp-wan in sync"
+  exit "$rc"
+fi
+
+[ -n "$VIP" ] || { echo "--vip is required to install" >&2; exit 2; }
+
+for f in $SCRIPTS; do
+  put "$HERE/$f" "/tmp/$f"
+  # root:vyattacfg 0775 -- vrrp-wan-apply enters config mode, which requires
+  # membership of vyattacfg.
+  run "sudo install -o root -g vyattacfg -m 0775 /tmp/$f /config/$f"
+done
+
+# Settings, with the VIP substituted. One file, read by BOTH the reconciler and
+# the health check -- keepalived invokes the latter with no environment at all,
+# so an Environment= line in the unit would be read by one and not the other.
+sed "s|^VRRP_WAN_VIP=.*|VRRP_WAN_VIP=${VIP}|" "$HERE/vrrp-wan.conf" > /tmp/vrrp-wan.conf.gen
+put /tmp/vrrp-wan.conf.gen /tmp/vrrp-wan.conf.gen
+run "sudo install -o root -g vyattacfg -m 0664 /tmp/vrrp-wan.conf.gen /config/vrrp-wan.conf"
+
+for f in $UNITS; do
+  put "$HERE/$f" "/tmp/$f"
+  run "sudo install -m 0644 /tmp/$f /etc/systemd/system/$f"
+done
+
+put "$HERE/ppp-vrrp-gate.conf" /tmp/ppp-vrrp-gate.conf
+run "sudo mkdir -p $GATE_DIR && sudo install -m 0644 /tmp/ppp-vrrp-gate.conf $GATE"
+
+run "sudo systemctl daemon-reload && sudo systemctl enable --now vrrp-wan-reconcile.timer vrrp-wan-guard.timer" >/dev/null 2>&1
+
+echo "  installed (vip=$VIP)"
+run "sudo /config/vrrp-wan-reconcile --status"

migration/vrrp-wan-reconcile

@@ -0,0 +1,278 @@
+#!/bin/sh
+# Make the WAN match VRRP mastership. Idempotent; safe to run every 30s and on
+# every VRRP transition.
+#
+# Two WANs, two different control planes, for a reason:
+#
+#   bond0.53 (10 gig, DHCP)  -- CONFIG plane. Its lease is bound to a cloned MAC
+#                               (f0:9f:c2:12:9b:4f, the old USG's), and only VyOS
+#                               config can move a MAC. One commit per failover.
+#   pppoe0   (Vodafone)      -- SYSTEMD plane. Gated by a drop-in on
+#                               ppp@pppoe0; see migration/ppp-vrrp-gate.conf.
+#                               No commit, no config lock, no `save`.
+#
+# PPPoE used to be on the config plane too, via `set interfaces pppoe pppoe0
+# disable`. That could not work: `disable` unlinks /etc/ppp/peers/pppoe0, which
+# is pppd's options file, so the promotion path deleted the very thing it needed
+# and left the unit restart-looping (observed: 47 restarts, zero sessions at the
+# access concentrator).
+#
+# Why a reconciler and not just transition scripts: VyOS delivers
+# `transition-script` through keepalived-fifo.py, and on 2026-09-02 that helper
+# logged NOTHING for a promotion while Keepalived_vrrp logged all six instances
+# entering MASTER. A router held every VIP with no WAN -- the outage, recreated
+# by the mechanism meant to prevent it. Scripts give speed; the timer gives
+# correctness.
+#
+#   vrrp-wan-reconcile          reconcile once
+#   vrrp-wan-reconcile --status what it thinks, changing nothing
+
+CONF=/config/vrrp-wan.conf
+[ -r "$CONF" ] && . "$CONF"
+VIP="${VRRP_WAN_VIP:-192.168.1.1}"
+WAN_VIF="${WAN_VIF:-53}"
+FLAP_MAX="${FLAP_MAX:-6}"
+FLAP_WINDOW="${FLAP_WINDOW:-600}"
+FLAP_HOLDOFF="${FLAP_HOLDOFF:-900}"
+
+STATE=/run/vrrp-wan
+LOCK=/run/vrrp-wan.lock
+APPLY=/config/vrrp-wan-apply
+DROPIN=/etc/systemd/system/ppp@pppoe0.service.d/10-vrrp-wan-gate.conf
+V6_TUNNEL="${V6_TUNNEL:-tun0}"
+RADVD_CONF="${RADVD_CONF:-/run/radvd/radvd.conf}"
+
+cfg() { /opt/vyatta/bin/vyatta-op-cmd-wrapper show configuration commands 2>/dev/null; }
+holds_vip()   { ip -4 -o addr show 2>/dev/null | grep -q " ${VIP}/"; }
+wan_up()      { ip -4 addr show "bond0.${WAN_VIF}" 2>/dev/null | grep -q 'inet '; }
+ppp_up()      { ip -4 addr show pppoe0 2>/dev/null | grep -q 'inet '; }
+ppp_active()  { systemctl is-active --quiet ppp@pppoe0 2>/dev/null; }
+lease_age()   { s=$(stat -c %Y "$STATE/may-dial" 2>/dev/null) || return 1
+                echo $(( $(date +%s) - s )); }
+
+# NOTE: there is deliberately no ppp_disabled(). pppoe0 is now ENABLED in config
+# on both routers, so such a test would be permanently false and the backup
+# early-exit below would never fire -- entering config mode every 30s for ever,
+# committing nothing. That exact shape was already live on the sim secondary,
+# whose /tmp/vrrp-wan-commit.log read "No configuration changes to commit" while
+# the script reported success.
+wan_disabled(){ cfg | grep -q "vif ${WAN_VIF} disable"; }
+
+if [ "${1:-}" = "--status" ]; then
+    printf 'vip=%s holds_vip=%s wan_disabled=%s wan_up=%s ppp_up=%s ppp_active=%s may_dial=%s lease_age=%s dropin=%s role=%s tun=%s radvd=%s\n' \
+        "$VIP" "$(holds_vip && echo yes || echo no)" \
+        "$(wan_disabled && echo yes || echo no)" \
+        "$(wan_up && echo yes || echo no)" \
+        "$(ppp_up && echo yes || echo no)" \
+        "$(ppp_active && echo yes || echo no)" \
+        "$([ -f "$STATE/may-dial" ] && echo yes || echo no)" \
+        "$(lease_age 2>/dev/null || echo -)" \
+        "$([ -f "$DROPIN" ] && echo yes || echo MISSING)" \
+        "$(cat "$STATE/role" 2>/dev/null || echo unset)" \
+        "$(ip -br link show "$V6_TUNNEL" 2>/dev/null | awk '{print $2}' || echo absent)" \
+        "$(systemctl is-active radvd 2>/dev/null || echo inactive)"
+    exit 0
+fi
+
+# One writer. The lock fd MUST be closed for children (`9>&-` on every call):
+# entering VyOS config mode spawns a long-lived unionfs-fuse for the session
+# which INHERITS the descriptor and never releases it, so from the first commit
+# onward every later run lost the flock and exited 0 having done nothing. That
+# is how a demoted router kept the WAN.
+exec 9>"$LOCK"
+flock -n 9 || exit 0
+
+mkdir -p "$STATE"
+
+# Reap config sessions whose owning process is gone. VyOS leaves a unionfs mount
+# per `configure`, one of them holds the commit lock, and after that EVERY commit
+# fails -- including the manual one you try in order to fix it.
+for d in /opt/vyatta/config/tmp/new_config_*; do
+    [ -d "$d" ] || continue
+    pid=${d##*_}
+    kill -0 "$pid" 2>/dev/null && continue
+    umount -l "$d" 2>/dev/null
+    rm -rf "$d" 2>/dev/null
+done
+
+# `show configuration commands` has been observed returning EMPTY transiently
+# under commit-lock contention. Every grep against it then reads false, which on
+# the master path looks like "the WAN is disabled" and triggers a pointless
+# commit -- one such spurious "releasing" was logged on a box where both WANs
+# were already in the right state. A real config is ~500 lines; refuse to act on
+# a suspiciously short one.
+if [ "$(cfg | wc -l)" -lt 50 ]; then
+    logger -t vrrp-wan "config read returned <50 lines; skipping this tick"
+    exit 0
+fi
+
+# --- PPPoE: the systemd plane ---------------------------------------------
+ppp_dial() {
+    # An ESTABLISHED session outranks every guard below, and this must be the
+    # first thing here. `may-dial` is a lease the guard expires after
+    # LEASE_TTL, so any early `return 1` before this renew silently hands the
+    # guard a live session to kill.
+    #
+    # Observed in labsim: the flap damper tripped, returned early, the lease
+    # went stale at 81s > 75s and the guard hung up pppoe0 ON THE MASTER --
+    # a damper meant to suppress repeat DIALS tore down a working WAN instead.
+    # Everything below only decides whether to start a NEW session.
+    if ppp_active; then
+        touch "$STATE/may-dial"
+        return 0
+    fi
+    # Refuse to bless a box whose gate is missing. /etc is per-image, so a VyOS
+    # upgrade silently drops the drop-in -- and without it BOTH routers dial on
+    # the next commit that touches the pppoe subtree. Failing closed turns a
+    # silent loss of protection into "PPPoE never comes up", the safe direction.
+    if [ ! -f "$DROPIN" ]; then
+        logger -t vrrp-wan "REFUSING to dial: gate drop-in $DROPIN is missing (VyOS upgrade?)"
+        return 1
+    fi
+    # The peers file is pppd's options file AND the gate's second condition, so
+    # without it this box silently never dials: systemd logs "skipped because of
+    # an unmet condition check" once and nothing else complains. Only a commit
+    # that touches the pppoe subtree re-renders it.
+    #
+    # Seen in labsim: config applied but never `save`d, the router rebooted, and
+    # came back with no pppoe0 node at all -- so no peers file, and a master that
+    # dialled every tick into silence. Say so loudly rather than looking healthy.
+    if [ ! -f /etc/ppp/peers/pppoe0 ]; then
+        if cfg | grep -q "interfaces pppoe pppoe0 source-interface"; then
+            logger -t vrrp-wan "CANNOT dial: pppoe0 is configured but /etc/ppp/peers/pppoe0 is missing -- re-commit the pppoe subtree to re-render it"
+        else
+            logger -t vrrp-wan "CANNOT dial: no pppoe0 in config (did a reboot revert an unsaved commit?)"
+        fi
+        return 1
+    fi
+    now=$(date +%s)
+    if [ -f "$STATE/holdoff" ] && [ "$now" -lt "$(cat "$STATE/holdoff" 2>/dev/null || echo 0)" ]; then
+        return 1
+    fi
+    touch "$STATE/may-dial"          # renew the lease every tick
+    # Trim the dial log to the window, then decide.
+    if [ -f "$STATE/dials" ]; then
+        awk -v c="$((now - FLAP_WINDOW))" '$1 > c' "$STATE/dials" > "$STATE/dials.new" 2>/dev/null
+        mv "$STATE/dials.new" "$STATE/dials" 2>/dev/null
+    fi
+    # `cat | wc`, not `wc -l < file`: the shell applies redirections left to
+    # right, so a missing file fails the `<` BEFORE `2>/dev/null` is in effect
+    # and dash prints "No such file or directory" on every first-ever dial.
+    if [ "$(cat "$STATE/dials" 2>/dev/null | wc -l)" -ge "$FLAP_MAX" ]; then
+        echo $((now + FLAP_HOLDOFF)) > "$STATE/holdoff"
+        logger -t vrrp-wan "DIAL FLAP: >=${FLAP_MAX} attempts in ${FLAP_WINDOW}s -- holding off ${FLAP_HOLDOFF}s"
+        return 1
+    fi
+    echo "$now" >> "$STATE/dials"
+    logger -t vrrp-wan "MASTER: dialling pppoe0"
+    systemctl reset-failed ppp@pppoe0 2>/dev/null
+    # `systemctl start` exits 0 even when a Condition blocks the start, so its
+    # return code proves nothing. is-active is the only honest answer.
+    systemctl start ppp@pppoe0 2>/dev/null
+}
+
+ppp_release() {
+    # Order matters: revoke the lease FIRST, then stop. The file's absence blocks
+    # any NEW start (including one a concurrent VyOS commit would trigger); the
+    # stop kills the process that already exists. Stopping first leaves a window
+    # in which a commit re-dials a box that is being demoted.
+    rm -f "$STATE/may-dial"
+    ppp_active || return 0
+    logger -t vrrp-wan "not MASTER: hanging up pppoe0"
+    systemctl stop ppp@pppoe0 2>/dev/null
+}
+
+# --- IPv6: the kernel plane -------------------------------------------------
+# The HE 6in4 tunnel and the VLAN 9 router advertisements have to follow
+# mastership too, or a failover keeps IPv4 and silently drops IPv6 -- the
+# partial outage that presents as "some sites are broken".
+#
+# A THIRD plane, and deliberately not either of the other two. Not config,
+# because nothing here needs a commit (unlike the cloned MAC) and a commit per
+# transition is the cost the pppoe0 half exists to avoid. Not the systemd gate,
+# because there is no equivalent of a peers file to destroy.
+#
+# What makes this cheap: the tunnel is anchored to 87.192.101.48, the 10 gig
+# lease bound to the cloned MAC, so it follows the VIP to the other router
+# UNCHANGED. A router-level failover therefore needs no HE API call at all --
+# only the link brought up on the box that now owns the address.
+#
+# Note what is deliberately NOT done here: this does not invoke
+# he-tunnel-follow. That script has its own 1-minute task-scheduler cadence and
+# a 2-tick hysteresis, and on 2026-09-06 that hysteresis was the only thing that
+# stopped a routine `vif53-pin-boot-disable` run from pointing HE at a PPPoE
+# address -- by 22 seconds. Calling it from a 30s reconciler as well would halve
+# the window it needs. Its job is the WITHIN-box fall back to PPPoE; ours is
+# link state.
+v6_take() {
+    # Absent on a router that has no tunnel in its config -- which is every
+    # router until the model change lands. No-op there rather than complain.
+    [ -e "/sys/class/net/$V6_TUNNEL" ] || return 0
+    # Needs SOME WAN address to source from. Either line will do: if bond0.53 is
+    # down but pppoe0 is up, he-tunnel-follow re-points the tunnel on its own
+    # schedule, and holding the link down until then would turn a degraded path
+    # into no path.
+    wan_up || ppp_up || return 0
+    ip link show "$V6_TUNNEL" 2>/dev/null | grep -q 'state DOWN' && {
+        logger -t vrrp-wan "MASTER: bringing $V6_TUNNEL up"
+        ip link set "$V6_TUNNEL" up 2>/dev/null
+    }
+    # radvd's config is rendered into /run by the VyOS commit, so on a box with
+    # no router-advert node there is nothing to start.
+    [ -f "$RADVD_CONF" ] || return 0
+    systemctl is-active --quiet radvd 2>/dev/null && return 0
+    logger -t vrrp-wan "MASTER: starting radvd"
+    systemctl start radvd 2>/dev/null
+}
+
+v6_release() {
+    [ -e "/sys/class/net/$V6_TUNNEL" ] || return 0
+    # radvd FIRST, and this ordering is the point: on a graceful stop it emits a
+    # final advertisement with router-lifetime 0, which is what tells VLAN 9
+    # hosts to stop using this box as their default router. Kill the daemon
+    # after tearing things down and they keep a dead gateway until the RA
+    # lifetime expires on its own.
+    if systemctl is-active --quiet radvd 2>/dev/null; then
+        logger -t vrrp-wan "not MASTER: stopping radvd (deprecates the v6 gateway)"
+        systemctl stop radvd 2>/dev/null
+    fi
+    ip link show "$V6_TUNNEL" 2>/dev/null | grep -q 'state DOWN' && return 0
+    logger -t vrrp-wan "not MASTER: bringing $V6_TUNNEL down"
+    ip link set "$V6_TUNNEL" down 2>/dev/null
+}
+
+# --- decide ----------------------------------------------------------------
+if holds_vip; then
+    echo master > "$STATE/role"
+    [ -f "$STATE/since" ] || date +%s > "$STATE/since"
+    ppp_dial
+    # The WAN block is now an `if` rather than an early exit, so the IPv6 plane
+    # below is reached on EVERY tick and not only on the one that enables the
+    # WAN. On the promotion tick bond0.53 has no address yet, so v6_take no-ops
+    # and the next tick takes it.
+    if wan_disabled; then
+        logger -t vrrp-wan "MASTER with bond0.${WAN_VIF} disabled -> enabling"
+        t0=$(date +%s)
+        "$APPLY" enable 9>&-
+        logger -t vrrp-wan "bond0.${WAN_VIF} enable commit took $(( $(date +%s) - t0 ))s"
+    fi
+    v6_take
+else
+    echo backup > "$STATE/role"
+    rm -f "$STATE/since" "$STATE/holdoff"
+    ppp_release
+    # Before the WAN goes, not after: once bond0.53 is disabled the source
+    # address is gone and radvd's farewell advertisement has no path out.
+    v6_release
+    if ! wan_disabled; then
+        logger -t vrrp-wan "not MASTER but bond0.${WAN_VIF} enabled -> releasing"
+        t0=$(date +%s)
+        "$APPLY" disable 9>&-
+        logger -t vrrp-wan "bond0.${WAN_VIF} disable commit took $(( $(date +%s) - t0 ))s"
+    fi
+fi
+
+# No `save`, deliberately. config.boot keeps `vif 53 disable` on BOTH routers, so
+# a reboot in any order comes up unable to claim the cloned MAC. PPPoE needs no
+# such convention any more: with the gate, config.boot is safe by construction
+# and a stray `save` cannot make both boxes dial.

migration/vrrp-wan-reconcile.service

@@ -0,0 +1,12 @@
+[Unit]
+# Belt to the transition scripts' braces. VyOS's keepalived-fifo.py helper was
+# observed dropping a MASTER transition silently, leaving a router holding every
+# VIP with no WAN. A timer cannot be dropped the same way.
+Description=Reconcile WAN interface state with VRRP mastership
+# vyos-router loads config at boot and its pppoe handler will try to dial; the
+# gate drop-in blocks that, but ordering after it keeps the logs readable.
+After=keepalived.service vyos-router.service
+
+[Service]
+Type=oneshot
+ExecStart=/config/vrrp-wan-reconcile

migration/vrrp-wan-reconcile.timer

@@ -0,0 +1,13 @@
+[Unit]
+Description=Reconcile WAN with VRRP mastership every 30s
+
+[Timer]
+# 30s: fast enough that a dropped transition is a blip rather than an outage,
+# slow enough that it is never the thing generating load. It only commits when
+# state actually disagrees, so a steady-state tick is two `ip` calls and a grep.
+OnBootSec=60
+OnUnitActiveSec=30
+AccuracySec=5
+
+[Install]
+WantedBy=timers.target

migration/vrrp-wan-release

@@ -0,0 +1,5 @@
+#!/bin/sh
+# VRRP transition hook. One code path: the reconciler derives everything from
+# ground truth, so take and release are the same operation asked at different
+# moments. Speed comes from here; correctness comes from the timer.
+exec /config/vrrp-wan-reconcile

migration/vrrp-wan-take

@@ -0,0 +1,5 @@
+#!/bin/sh
+# VRRP transition hook. One code path: the reconciler derives everything from
+# ground truth, so take and release are the same operation asked at different
+# moments. Speed comes from here; correctness comes from the timer.
+exec /config/vrrp-wan-reconcile

migration/vrrp-wan.conf

@@ -0,0 +1,71 @@
+# Settings for the vrrp-wan scripts. Installed to /config/vrrp-wan.conf.
+#
+# Why a file and not systemd Environment=: keepalived invokes vrrp-wan-health
+# with NO environment at all, so an Environment= line in the .service would be
+# read by the reconciler and ignored by the health check -- two sources of truth
+# for the one value that decides who is master. It is also what stops a repeat
+# of 2026-09-05, when the sim's proof was obtained from scripts hand-`sed`-ed in
+# place: /config/vrrp-wan-health differed from git, and a reinstall would have
+# silently reverted the tested behaviour.
+
+# The management VIP. "Do I hold this address" IS the definition of master here
+# -- ground truth, not a marker written by a script that may not have run.
+VRRP_WAN_VIP=192.168.1.1
+
+# The DHCP WAN sub-interface. Stays on the config plane because its lease is
+# bound to a cloned MAC, which only VyOS config can move.
+WAN_VIF=53
+
+# Seconds a new master may go without any WAN before the health check fails it.
+#
+# Must exceed the ISP's stale-session hold-down, or a hard failover blows the
+# window and BOTH routers end up in FAULT -- worse than the outage the check
+# exists to prevent.
+#
+# MEASURED, labsim T4, master destroyed with `virsh destroy`, time until the
+# survivor held a PPPoE session (labsim/wan-failover-evidence/T4-*). Two
+# independent runs, so these are the AC's behaviour rather than one-offs:
+#
+#     session-control=replace    26s / 26s
+#     session-control=deny      148s / 141s   <-- worst
+#     session-control=disable    21s / 20s
+#
+# `deny` is the hostile case and the only one that matters for sizing: the AC
+# refuses the survivor until its own dead-peer timer frees the dead session.
+# The poller caught it happening -- the destroyed router's session stayed in the
+# table while the survivor's dial attempts appeared and were rejected, twice,
+# before it finally got in at 148s.
+#
+# 148s also lands well past the theoretical lcp-echo-interval(30) x
+# failure(3) = 90s budget that 180 was originally sized against, which left only
+# 32s of margin. 300 gives roughly 2x the worst observed, on IDLE 2-vCPU sim
+# VMs; the VP2440s under kea, BGP and conntrack will be slower, and Vodafone's
+# actual policy and timers are unknown.
+#
+# The cost is real and worth stating: this is also how long a master that is
+# alive but genuinely cannot route keeps holding every VIP before yielding --
+# the 2026-09-02 outage shape. That case is mostly covered by bond0.53, which
+# satisfies the check within seconds of getting a DHCP lease; GRACE only
+# dominates when PPPoE is the only path left.
+#
+# Do not lower this below the worst measured handover without re-running
+# `labsim/labsim-pppoe-ha-test.sh --hard`. Before 2026-09-06 that matrix never
+# actually set session-control and reported `deny` at 25s -- a number that did
+# not exist.
+GRACE=300
+
+# may-dial is a LEASE, not a flag. vrrp-wan-reconcile renews its mtime every
+# tick; vrrp-wan-guard revokes it once it goes stale. A plain flag survives the
+# reconciler dying, and a router that stops reconciling while demoted would keep
+# dialling for ever.
+LEASE_TTL=75
+
+# Flap damper. Two routers that both believe they hold the VIP (a VRRP
+# partition) will both dial; with the AC set to `replace` each dial kills the
+# other's session, the loser's pppd exits non-zero, systemd redials in 5s, and
+# the pair hammers the access concentrator indefinitely. Against a real ISP that
+# is how an account gets rate-limited. More than FLAP_MAX dials in FLAP_WINDOW
+# puts this box in hold-off and logs loudly.
+FLAP_MAX=6
+FLAP_WINDOW=600
+FLAP_HOLDOFF=900

migration/vyos-known-good

@@ -0,0 +1,120 @@
+#!/bin/vbash
+# Pin a config you have SEEN working, and get back to it with one command.
+#
+# Why this exists when VyOS already has rollback: `rollback 1` returns you to the
+# previous revision, which may itself be broken -- you can walk backwards through
+# several bad commits looking for the one that worked. This pins a state you
+# explicitly confirmed was good, so recovery is one step and does not require
+# remembering how many changes ago things last worked.
+#
+# It is deliberately NOT automatic. A config is only "known good" once a human
+# has used the network and found it working; a script cannot judge that, and a
+# snapshot taken automatically after every commit would faithfully preserve the
+# broken one.
+#
+#   vyos-known-good save      mark the running config as known-good
+#   vyos-known-good status    when it was taken, and how it differs from running
+#   vyos-known-good restore   go back to it (commit-confirmed, so even this is safe)
+#   vyos-known-good diff      what would change if you restored
+#
+# Lives in /config so it survives image upgrades, like vyos-unifi-switch.
+
+# Capture the arguments BEFORE sourcing script-template: sourcing it resets the
+# positional parameters, so $1 is empty by the time the case statement runs and
+# every invocation silently falls through to the usage message.
+ACTION="${1:-status}"
+
+source /opt/vyatta/etc/functions/script-template
+
+GOOD="/config/known-good.boot"
+META="/config/known-good.meta"
+RUNNING="/config/config.boot"
+CONFIRM_MINUTES="${CONFIRM_MINUTES:-5}"
+
+say()  { printf '\033[0;36m[known-good]\033[0m %s\n' "$*"; }
+warn() { printf '\033[1;33m[known-good]\033[0m %s\n' "$*" >&2; }
+die()  { printf '\033[0;31m[known-good]\033[0m %s\n' "$*" >&2; exit 1; }
+
+# The running config on disk is only current if nothing is uncommitted-and-unsaved.
+# Saving a snapshot that does not match what is actually running would be worse
+# than having no snapshot at all -- it would look like a safety net and not be one.
+require_saved() {
+  if ! cli-shell-api sessionChanged >/dev/null 2>&1; then
+    return 0
+  fi
+  die "there are uncommitted changes; commit and save first, or this snapshot would not match reality"
+}
+
+cmd_save() {
+  require_saved
+  [ -r "$RUNNING" ] || die "cannot read $RUNNING"
+  sudo cp "$RUNNING" "$GOOD"
+  # 0660 root:vyattacfg, matching /config/config.boot. 0600 would make the
+  # snapshot unreadable to the vyos user, so `status` and `diff` -- the two you
+  # run while deciding whether to restore -- would silently show nothing.
+  sudo chmod 0660 "$GOOD"; sudo chgrp vyattacfg "$GOOD"
+  sudo chmod 0660 "$META" 2>/dev/null; sudo chgrp vyattacfg "$META" 2>/dev/null
+  {
+    echo "saved_at=$(date -Is)"
+    echo "saved_by=${SUDO_USER:-$USER}"
+    echo "hostname=$(hostname)"
+    echo "lines=$(wc -l < "$RUNNING")"
+  } | sudo tee "$META" >/dev/null
+  say "pinned $(wc -l < "$GOOD") lines as known-good on $(hostname)"
+  say "restore with: /config/vyos-known-good restore"
+}
+
+cmd_status() {
+  [ -r "$GOOD" ] || { warn "no known-good snapshot on $(hostname) -- run 'save' while things work"; return 1; }
+  say "known-good on $(hostname):"
+  sed 's/^/    /' "$META" 2>/dev/null
+  local n
+  n="$(diff <(grep -vE '^\s*$' "$GOOD") <(grep -vE '^\s*$' "$RUNNING") 2>/dev/null | grep -c '^[<>]')"
+  if [ "${n:-0}" -eq 0 ]; then
+    say "running config MATCHES known-good"
+  else
+    warn "running config differs from known-good by $n line(s) -- 'diff' to see them"
+  fi
+}
+
+cmd_diff() {
+  [ -r "$GOOD" ] || die "no known-good snapshot"
+  diff -u "$GOOD" "$RUNNING" | sed -E "s/(password|key|secret)[[:space:]]+\S+/\1 <REDACTED>/I" || true
+}
+
+cmd_restore() {
+  [ -r "$GOOD" ] || die "no known-good snapshot to restore"
+  say "restoring known-good on $(hostname) (taken $(grep -m1 saved_at "$META" 2>/dev/null | cut -d= -f2-))"
+
+  # Commit-confirmed even here. If the known-good snapshot is itself somehow
+  # wrong, or the restore cannot be confirmed because access is still broken,
+  # the router undoes it rather than leaving you worse off. Silence reverts.
+  local script; script="$(mktemp)"
+  {
+    echo 'source /opt/vyatta/etc/functions/script-template'
+    echo 'configure'
+    echo "load $GOOD"
+    printf 'sudo sg vyattacfg "/usr/bin/config-mgmt commit_confirm -y -t=%s"\n' "$CONFIRM_MINUTES"
+    echo 'export IN_COMMIT_CONFIRM=t'
+    echo 'commit'
+    echo 'unset IN_COMMIT_CONFIRM'
+    echo 'exit'
+  } > "$script"
+  vbash "$script"; local rc=$?
+  rm -f "$script"
+
+  [ $rc -eq 0 ] || die "restore failed (rc=$rc) -- nothing was committed"
+  say ""
+  say "RESTORED under a ${CONFIRM_MINUTES} minute timer."
+  say "Check the network NOW. If it works, confirm it:"
+  say "    sudo sg vyattacfg '/usr/bin/config-mgmt confirm'"
+  say "If you do nothing, the router reverts on its own."
+}
+
+case "$ACTION" in
+  save)    cmd_save ;;
+  status)  cmd_status ;;
+  diff)    cmd_diff ;;
+  restore) cmd_restore ;;
+  *) die "usage: vyos-known-good {save|status|diff|restore}" ;;
+esac

migration/vyos-mode-delta.py

@@ -0,0 +1,507 @@
+#!/usr/bin/env python3
+"""Generate the delta that turns a passive VyOS pair into the gateway.
+
+The switch works as: load the known-good `unifi.boot` snapshot, apply this
+delta, commit-confirm. Deriving the gateway mode from base+delta every time
+means there is no inverse to maintain and no drift between two hand-kept
+configs -- the revert is just loading the snapshot again.
+
+  ./vyos-mode-delta.py --priority 200 -o to-vyos.commands     # vyos001 (master)
+  ./vyos-mode-delta.py --priority 100 -o to-vyos.commands     # vyos002 (backup)
+  ./vyos-mode-delta.py --emit-secrets /path/wan-secrets       # credentials, 0600
+
+The PPPoE password is NOT written into the delta. The delta carries the
+placeholder @@WAN_PASSWORD@@ and the switch script substitutes it at apply time
+from /config/wan-secrets, so the generated artifact can be read, diffed and
+copied around without carrying a credential.
+"""
+from __future__ import annotations
+
+import argparse
+import importlib.util
+import ipaddress
+import json
+import os
+import sys
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+
+# unifi-to-vyos.py has hyphens, so it cannot be imported by name. Reuse it
+# rather than duplicating the DHCP/DNS generation -- the whole point is that
+# what labsim proved and what production gets come from one code path.
+_spec = importlib.util.spec_from_file_location(
+    "unifi_to_vyos", os.path.join(HERE, "unifi-to-vyos.py"))
+unifi_to_vyos = importlib.util.module_from_spec(_spec)
+_spec.loader.exec_module(unifi_to_vyos)
+
+# Two WANs, established by reading the live USG rather than the UniFi fields
+# (which report wan_type=dhcp for both and are simply wrong):
+#
+#   WAN1  Vodafone, PPPoE on the USG's eth0, ~900/700 Mbit. Verified working:
+#         pppoe0 came up with 90.241.226.213 peer 84.65.128.1, MTU 1492.
+#   WAN2  10 gig ISP, plain DHCP on the USG's eth2, public 87.192.101.48/21
+#         gw 87.192.96.1. This is what carries traffic today.
+#
+# Both reach the USG as untagged access ports but are carried across the switch
+# fabric as vlan-only networks 51 and 53, so VyOS picks them up as bond vifs.
+WAN_PPPOE_VIF = "bond0.51"      # Vodafone
+WAN_PPPOE_IF = "pppoe0"
+WAN_DHCP_VIF = "bond0.53"       # 10 gig ISP
+
+# The DHCP lease is bound to the MAC, so cloning the USG's WAN2 MAC is how VyOS
+# keeps 87.192.101.48 instead of negotiating a fresh lease -- or getting none,
+# if the ISP hands out one per line. Only ONE box may carry this at a time.
+WAN_DHCP_MAC = "f0:9f:c2:12:9b:4f"
+
+# Route distances: the 10 gig line wins, Vodafone is failover.
+#
+# The live 10 gig default route is owned by `protocols failover`, so that losing
+# the ISP *without* losing carrier withdraws it instead of black-holing every
+# packet -- a DHCP-installed route never withdraws on a dead upstream.
+#
+# The vif still needs default-route-distance rather than no-default-route:
+# vyos-failover resolves a dhcp-interface gateway by reading new_routers out of
+# /run/dhclient/dhclient_<if>.lease, and no-default-route leaves that field
+# EMPTY, so the daemon finds no next hop and installs nothing. Verified on
+# vyos001: with no-default-route the default route fell through to Vodafone.
+#
+# So DHCP keeps a route, deliberately demoted BELOW Vodafone. Order of
+# preference: failover's kernel route (distance 0) > pppoe (10) > DHCP (210).
+# The demoted route is never selected while pppoe is up, so it cannot re-create
+# the black-hole it exists to avoid.
+DIST_PPPOE = 10
+DIST_DHCP_FALLBACK = 210
+
+# Health-checked primary. Two targets, any-available, so one resolver having a
+# bad day is not read as "the line is down". Verified on the sim: failover and
+# failback both inside 5s with the router's own interface still UP.
+FAILOVER_METRIC = 1
+FAILOVER_TARGETS = ["8.8.8.8", "1.1.1.1"]
+FAILOVER_TIMEOUT = 5
+
+PLACEHOLDER = "@@WAN_PASSWORD@@"
+
+# Per-VLAN interface addresses of each node, read from the live boxes. VRRP
+# unicast (hello-source-address/peer-address) needs both ends explicitly, and
+# these are NOT derivable from the subnet -- VLAN 3 is .4/.5 while everything
+# else is .252/.253.
+#                vlan: (vyos001,          vyos002)
+NODE_ADDRS = {
+    1:   ("192.168.1.252", "192.168.1.253"),
+    2:   ("192.168.9.252", "192.168.9.253"),
+    3:   ("192.168.3.4",   "192.168.3.5"),
+    9:   ("10.8.0.252",    "10.8.0.253"),
+    10:  ("10.0.1.252",    "10.0.1.253"),
+    200: ("192.168.2.252", "192.168.2.253"),
+}
+
+# Dedicated point-to-point link for conntrack state sync (eth3 <-> eth3).
+CONNTRACK_ADDRS = ("10.255.255.1/30", "10.255.255.2/30")
+CONNTRACK_IF = "eth3"
+
+# kea HA talks over TCP 647. The LoT addresses are used because they are stable
+# and reachable today without the conntrack cable being plugged in.
+DHCP_HA_NAME = "vyos-dhcp-pair"     # must NOT equal either system host-name
+
+
+
+def vrrp_group(vlan: int) -> str:
+    """VRRP group names as configured on the boxes: 'native' for the untagged
+    VLAN, 'vlan<id>' otherwise."""
+    return "native" if vlan == 1 else f"vlan{vlan}"
+
+
+def build_delta(inv: dict, priority: int, wan_user: str, with_wan: bool,
+                conntrack_link: bool) -> list[str]:
+    out: list[str] = []
+    primary = priority >= 200          # vyos001 is the master/primary
+    self_i, peer_i = (0, 1) if primary else (1, 0)
+    nets = [n for n in inv["networks"] if n["dhcp_enabled"] and n["subnet"]]
+    nets.sort(key=unifi_to_vyos.vlan_of)
+
+    out += [
+        "# ==========================================================",
+        "# Delta: passive VyOS pair -> gateway. Applied on top of a",
+        "# freshly loaded unifi.boot, never on top of itself.",
+        "# ==========================================================",
+        "",
+        "# An unconfirmed commit must reload the previous config, NOT reboot.",
+        "# 'reboot' is the VyOS default and would turn a failed switch into a",
+        "# real outage on the box that is meant to be carrying the network.",
+        "set system config-management commit-confirm action reload",
+        "",
+        "# --- gateway addresses ------------------------------------",
+        "# The VIP takes over the address the USG holds today, so no client",
+        "# changes anything: no renewal needed, hardcoded gateways keep working.",
+    ]
+    for n in nets:
+        vlan = unifi_to_vyos.vlan_of(n)
+        grp = vrrp_group(vlan)
+        iface = ipaddress.ip_interface(n["subnet"])
+        out.append(f"# {n['name']} (VLAN {vlan}) -> {iface.with_prefixlen}")
+        # Delete the whole address node rather than a computed old value.
+        # `address` is multi-value, and the current VIPs are NOT at
+        # network+254 on the /23 networks -- they are 192.168.9.254,
+        # 10.0.9.254 and 10.0.1.254, in the upper half. A delete naming the
+        # wrong address fails quietly and leaves the group holding two VIPs.
+        out.append(f"delete high-availability vrrp group {grp} address")
+        out.append(f"set high-availability vrrp group {grp} address {iface.with_prefixlen}")
+        out.append(f"set high-availability vrrp group {grp} priority {priority}")
+        own, peer = NODE_ADDRS[vlan] if primary else NODE_ADDRS[vlan][::-1]
+        # Unicast VRRP: the walkthrough sets both ends explicitly rather than
+        # relying on multicast, which is more predictable across a switch fabric.
+        out.append(f"set high-availability vrrp group {grp} hello-source-address {own}")
+        out.append(f"set high-availability vrrp group {grp} peer-address {peer}")
+        # Without no-preempt a recovered box reclaims the VIP immediately --
+        # before conntrack state has synced -- and drops every established
+        # connection. If preemption is ever wanted, preempt-delay must be >=
+        # the conntrack-sync purge-timeout.
+        out.append(f"set high-availability vrrp group {grp} no-preempt")
+
+    out += [
+        "",
+    ]
+
+
+    out += [
+        "",
+        "# --- stateful tracking (BOTH boxes) ------------------------",
+        "# VyOS only engages conntrack when a firewall or NAT exists. The",
+        "# backup has no WAN and therefore no NAT, so without this rule it",
+        "# tracks nothing -- and conntrack-sync entries replicated to a box",
+        "# whose conntrack is not engaged cannot be used when it takes over.",
+        "# Verified in labsim: zero conntrack entries until a state-matching",
+        "# rule was present, then replication began immediately.",
+        "set firewall ipv4 forward filter default-action accept",
+        "set firewall ipv4 forward filter rule 10 action accept",
+        "set firewall ipv4 forward filter rule 10 state established",
+        "set firewall ipv4 forward filter rule 10 state related",
+        "set firewall ipv4 forward filter rule 10 description 'stateful tracking'",
+    ]
+
+    if True:  # WAN config on BOTH boxes; see the disable block below
+        out += [
+            "# --- WAN -----------------------------------------------",
+            "# Both vifs must be created before anything references them.",
+            "# Neither firewall has vif 51 or 53 today (only 2, 3, 9, 10, 200),",
+            "# and pppoe source-interface points at an interface that must",
+            "# already exist -- without this the commit fails and, since the",
+            "# delta commits as one unit, takes the whole switch with it.",
+            f"set interfaces bonding bond0 vif {WAN_PPPOE_VIF.split('.')[1]} description 'WAN1 Vodafone (PPPoE)'",
+            f"set interfaces bonding bond0 vif {WAN_DHCP_VIF.split('.')[1]} description 'WAN2 10gig ISP (DHCP)'",
+            "",
+            "# WAN2, the 10 gig line -- primary. The cloned MAC is what keeps",
+            "# the existing public lease (87.192.101.48) instead of asking for",
+            "# a new one. Only the box carrying the WAN may set this.",
+            f"set interfaces bonding bond0 vif {WAN_DHCP_VIF.split('.')[1]} mac '{WAN_DHCP_MAC}'",
+            f"set interfaces bonding bond0 vif {WAN_DHCP_VIF.split('.')[1]} address dhcp",
+            # Demoted below Vodafone; `protocols failover` owns the live route.
+            # NOT no-default-route -- that blanks new_routers in the lease and
+            # leaves the failover daemon with no gateway to install.
+            f"set interfaces bonding bond0 vif {WAN_DHCP_VIF.split('.')[1]} dhcp-options default-route-distance {DIST_DHCP_FALLBACK}",
+            "",
+            "# WAN1, Vodafone -- failover at a higher distance. Verified working",
+            "# on the USG: pppoe0 came up with a public address, MTU 1492.",
+            f"set interfaces pppoe {WAN_PPPOE_IF} source-interface {WAN_PPPOE_VIF}",
+            f"set interfaces pppoe {WAN_PPPOE_IF} authentication username '{wan_user}'",
+            f"set interfaces pppoe {WAN_PPPOE_IF} authentication password '{PLACEHOLDER}'",
+            f"set interfaces pppoe {WAN_PPPOE_IF} mtu 1492",
+            f"set interfaces pppoe {WAN_PPPOE_IF} default-route-distance {DIST_PPPOE}",
+            # The peer's resolvers would otherwise overwrite resolv.conf.
+            f"set interfaces pppoe {WAN_PPPOE_IF} no-peer-dns",
+            "",
+            "# The static default route exists only for unifi mode, where the",
+            "# USG is the next hop. Both WANs supply one here.",
+            "delete protocols static route 0.0.0.0/0",
+            "",
+            "# --- Health-checked primary ----------------------------",
+            "# Without this, failover only fires when bond0.53 loses carrier",
+            "# or its lease. An ISP that keeps the link up while dropping",
+            "# traffic -- the common failure -- would black-hole everything,",
+            "# because a DHCP-installed route has nothing to withdraw it.",
+            "#",
+            "# vyos-failover pings each target bound to the interface",
+            "# (`ping -I bond0.53`), so the backup can never be validated",
+            "# through the primary's path and vice versa. On withdrawal the",
+            "# kernel falls through to Vodafone's distance-10 route.",
+            f"set protocols failover route 0.0.0.0/0 dhcp-interface {WAN_DHCP_VIF} check type icmp",
+            f"set protocols failover route 0.0.0.0/0 dhcp-interface {WAN_DHCP_VIF} check policy any-available",
+            f"set protocols failover route 0.0.0.0/0 dhcp-interface {WAN_DHCP_VIF} check timeout {FAILOVER_TIMEOUT}",
+            f"set protocols failover route 0.0.0.0/0 dhcp-interface {WAN_DHCP_VIF} metric {FAILOVER_METRIC}",
+            *[
+                f"set protocols failover route 0.0.0.0/0 dhcp-interface {WAN_DHCP_VIF} check target {t}"
+                for t in FAILOVER_TARGETS
+            ],
+            "",
+            "# --- NAT -----------------------------------------------",
+            f"set nat source rule 100 outbound-interface name {WAN_DHCP_VIF}",
+            "set nat source rule 100 translation address masquerade",
+            "set nat source rule 100 description 'LAN out via the 10gig line'",
+            f"set nat source rule 110 outbound-interface name {WAN_PPPOE_IF}",
+            "set nat source rule 110 translation address masquerade",
+            "set nat source rule 110 description 'LAN out via Vodafone (failover)'",
+        ]
+
+    if not with_wan:
+        # Both boxes carry the identical WAN and NAT config; only the RESTING
+        # STATE differs, and only for the DHCP line. Takeover is no longer a
+        # human deleting two lines under pressure -- vrrp-wan-reconcile does it,
+        # driven by who holds the management VIP. See migration/PPPOE-HA.md.
+        #
+        # bond0.53 stays here, on the CONFIG plane, because its lease is bound
+        # to a cloned MAC and only VyOS config can move a MAC between boxes.
+        # This is the "nothing to follow" default: a freshly built or PXE'd box
+        # has no live master to imitate, so it must come up unable to claim that
+        # MAC. On a running pair the model follows reality instead -- see the
+        # export-before-apply rule in migration/PPPOE-HA.md.
+        #
+        # pppoe0 is deliberately NOT disabled here any more. `disable` unlinks
+        # /etc/ppp/peers/pppoe0, which is pppd's own options file, so it
+        # destroys what the promotion path needs and leaves ppp@pppoe0
+        # restart-looping. Dialling is gated at the systemd unit instead.
+        #
+        # ORDERING TRAP for a rebuilt box: because pppoe0 is left ENABLED,
+        # interfaces_pppoe.py will try to dial on the first commit that touches
+        # the pppoe subtree. Install the gate FIRST --
+        # `migration/vrrp-wan-install --vip <mgmt VIP> --host vyos@<box>` --
+        # or the new box will take the single ISP session off the live master.
+        #
+        # NAT rules naming a down interface are harmless: VyOS warns at commit
+        # ("Interface ... does not exist!") and commits anyway, verified.
+        out += [
+            "",
+            "# --- 10 gig held DOWN on this box --------------------------",
+            "# Do NOT enable by hand: vrrp-wan-reconcile owns this, keyed on",
+            "# whoever holds the management VIP. pppoe0 is gated at the unit",
+            "# (ppp@pppoe0.service.d/10-vrrp-wan-gate.conf), not in config.",
+            f"set interfaces bonding bond0 vif {WAN_DHCP_VIF.split('.')[1]} disable",
+        ]
+
+    if True:
+        # Port forwards and the WAN firewall go on BOTH boxes. They name
+        # interfaces that are present-but-disabled on the backup, which VyOS
+        # accepts (it warns and commits). Putting them here means a failover is
+        # enabling an interface, not reconstructing NAT under pressure.
+        # Port forwards, straight from UniFi.
+        for i, p in enumerate(inv["port_forwards"]):
+            if not p.get("enabled"):
+                continue
+            rule = 100 + i * 10
+            proto = p["proto"]  # tcp | udp | tcp_udp -- all valid VyOS values
+            out += [
+                "",
+                f"set nat destination rule {rule} description '{p['name']}'",
+                f"set nat destination rule {rule} inbound-interface name {WAN_DHCP_VIF}",
+                f"set nat destination rule {rule} protocol {proto}",
+                f"set nat destination rule {rule} destination port '{p['dst_port']}'",
+                f"set nat destination rule {rule} translation address {p['fwd']}",
+            ]
+            # `destination port` accepts a comma list but `translation port` does
+            # NOT -- "16881,6881 is not a valid service name" -- because mapping a
+            # list onto a list is ambiguous. Every forward here maps a port to
+            # itself, and omitting translation port makes VyOS preserve the
+            # original, which is exactly right. Only emit it when it genuinely
+            # differs, and refuse rather than guess when a differing list appears.
+            if p["fwd_port"] != p["dst_port"]:
+                if "," in str(p["fwd_port"]) or "," in str(p["dst_port"]):
+                    raise SystemExit(
+                        f"port forward '{p['name']}' remaps a LIST of ports "
+                        f"({p['dst_port']} -> {p['fwd_port']}). VyOS cannot express "
+                        f"that in one rule; split it into one rule per port by hand.")
+                out.append(f"set nat destination rule {rule} translation port '{p['fwd_port']}'")
+
+        out += [
+            "",
+            "# --- firewall ----------------------------------------------",
+            "# VyOS defaults to accepting everything. The USG has an implicit",
+            "# WAN drop, so migrating the port forwards alone would leave the",
+            "# router's own services and the whole LAN reachable from the WAN.",
+            "#",
+            "# Scoped to the WAN interface rather than a global default-action",
+            "# drop: that way a mistake here cannot lock anyone out over the LAN,",
+            "# which is the only path back in during a cutover.",
+            "",
+            "# Traffic TO the router.",
+            "set firewall ipv4 input filter default-action accept",
+            "set firewall ipv4 input filter rule 100 action accept",
+            "set firewall ipv4 input filter rule 100 state established",
+            "set firewall ipv4 input filter rule 100 state related",
+            "set firewall ipv4 input filter rule 100 description 'established/related'",
+        ]
+        # The two WAN_LOCAL accepts carried over from UniFi.
+        out += [
+            "",
+            "set firewall ipv4 input filter rule 110 action accept",
+            "set firewall ipv4 input filter rule 110 protocol esp",
+            f"set firewall ipv4 input filter rule 110 inbound-interface name {WAN_DHCP_VIF}",
+            "set firewall ipv4 input filter rule 110 description 'VPN accept ESP (from UniFi WAN_LOCAL)'",
+            "",
+            "set firewall ipv4 input filter rule 120 action accept",
+            "set firewall ipv4 input filter rule 120 protocol udp",
+            "set firewall ipv4 input filter rule 120 destination port '500,4500'",
+            f"set firewall ipv4 input filter rule 120 inbound-interface name {WAN_DHCP_VIF}",
+            "set firewall ipv4 input filter rule 120 description 'VPN accept UDP500/4500 (from UniFi WAN_LOCAL)'",
+            "",
+            "set firewall ipv4 input filter rule 130 action accept",
+            "set firewall ipv4 input filter rule 130 protocol icmp",
+            f"set firewall ipv4 input filter rule 130 inbound-interface name {WAN_DHCP_VIF}",
+            "set firewall ipv4 input filter rule 130 description 'ICMP to the router (path MTU discovery)'",
+            "",
+            "# Everything else arriving from the WAN is dropped. LAN is untouched.",
+            "set firewall ipv4 input filter rule 900 action drop",
+            f"set firewall ipv4 input filter rule 900 inbound-interface name {WAN_DHCP_VIF}",
+            f"set firewall ipv4 input filter rule 910 action drop",
+            f"set firewall ipv4 input filter rule 910 inbound-interface name {WAN_PPPOE_IF}",
+            "set firewall ipv4 input filter rule 910 description 'drop all other WAN-to-router (Vodafone)'",
+            "set firewall ipv4 input filter rule 900 description 'drop all other WAN-to-router'",
+            "",
+            "# Traffic THROUGH the router.",
+            "set firewall ipv4 forward filter default-action accept",
+            "set firewall ipv4 forward filter rule 100 action accept",
+            "set firewall ipv4 forward filter rule 100 state established",
+            "set firewall ipv4 forward filter rule 100 state related",
+            "set firewall ipv4 forward filter rule 100 description 'established/related'",
+        ]
+
+        # Destination NAT happens before the forward filter, so these rules must
+        # match the translated destination, not the WAN address.
+        for i, p in enumerate(inv["port_forwards"]):
+            if not p.get("enabled"):
+                continue
+            rule = 200 + i * 10
+            out += [
+                "",
+                f"set firewall ipv4 forward filter rule {rule} action accept",
+                f"set firewall ipv4 forward filter rule {rule} inbound-interface name {WAN_DHCP_VIF}",
+                f"set firewall ipv4 forward filter rule {rule} protocol {p['proto']}",
+                f"set firewall ipv4 forward filter rule {rule} destination address {p['fwd']}",
+                f"set firewall ipv4 forward filter rule {rule} destination port '{p['fwd_port']}'",
+                f"set firewall ipv4 forward filter rule {rule} description 'port forward: {p['name']}'",
+            ]
+
+        out += [
+            "",
+            "# New inbound connections from the WAN that are not a port forward.",
+            "set firewall ipv4 forward filter rule 900 action drop",
+            f"set firewall ipv4 forward filter rule 900 inbound-interface name {WAN_DHCP_VIF}",
+            f"set firewall ipv4 forward filter rule 910 action drop",
+            f"set firewall ipv4 forward filter rule 910 inbound-interface name {WAN_PPPOE_IF}",
+            "set firewall ipv4 forward filter rule 910 description 'drop unsolicited WAN-to-LAN (Vodafone)'",
+            "set firewall ipv4 forward filter rule 900 description 'drop unsolicited WAN-to-LAN'",
+            "",
+        ]
+
+
+    # --- DHCP high-availability -------------------------------------------
+    # Without this BOTH boxes run kea on the same VLANs and race to answer the
+    # same broadcasts, handing different pool addresses to the same client.
+    # active-passive so only the primary serves, matching the VRRP shape.
+    dhcp_self, dhcp_peer = NODE_ADDRS[10][self_i], NODE_ADDRS[10][peer_i]
+    out += [
+        "",
+        "# --- DHCP high-availability --------------------------------",
+        "# Peers sync leases over TCP 647. Each subnet already carries a",
+        "# unique subnet-id (keyed on VLAN id), which kea HA requires.",
+        "set service dhcp-server high-availability mode active-passive",
+        f"set service dhcp-server high-availability status {'primary' if primary else 'secondary'}",
+        # The peer name must not collide with either system host-name.
+        f"set service dhcp-server high-availability name {DHCP_HA_NAME}",
+        f"set service dhcp-server high-availability source-address {dhcp_self}",
+        f"set service dhcp-server high-availability remote {dhcp_peer}",
+    ]
+
+    if conntrack_link:
+        # Stateful failover. Without it VRRP moves the address but every
+        # established connection dies, because the backup has no conntrack
+        # table. Needs the eth3 <-> eth3 cable physically present.
+        out += [
+            "",
+            "# --- conntrack-sync ----------------------------------------",
+            "# Dedicated point-to-point link: sync traffic must not compete",
+            "# with production, and must not die when the LAN does.",
+            f"set interfaces ethernet {CONNTRACK_IF} address {CONNTRACK_ADDRS[self_i]}",
+            f"set interfaces ethernet {CONNTRACK_IF} description 'conntrack-sync peer link'",
+            f"set service conntrack-sync interface {CONNTRACK_IF}",
+            "set service conntrack-sync failover-mechanism vrrp sync-group MAIN",
+            "set service conntrack-sync accept-protocol tcp",
+            "set service conntrack-sync accept-protocol udp",
+            "set service conntrack-sync accept-protocol icmp",
+            "set service conntrack-sync mcast-group 225.0.0.50",
+        ]
+
+    # DHCP + DNS, from the same generator labsim proved.
+    dhcp_lines, stats = unifi_to_vyos.build(inv, "prod")
+    expected = len(inv["reservations"])
+    if stats["mappings"] != expected:
+        raise SystemExit(
+            f"refusing to generate: {expected - stats['mappings']} reservation(s) "
+            f"missing -- every one must survive the cutover")
+    out += dhcp_lines
+    return out
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--priority", type=int, required=True,
+                    help="VRRP priority: 200 for the master, 100 for the backup")
+    ap.add_argument("--inventory", default=os.path.join(HERE, "export", "inventory.json"))
+    ap.add_argument("--raw-networkconf", default=os.path.join(HERE, "export", "rest_networkconf.json"))
+    ap.add_argument("--with-wan", action="store_true",
+                help="configure the WAN on this box. Only ONE of the pair may have\n                      it, because the cloned WAN MAC must be unique.")
+    ap.add_argument("--conntrack-link", action="store_true",
+                    help="emit conntrack-sync over the eth3 peer link. Requires the\n                          cable to be physically present on both boxes.")
+    ap.add_argument("-o", "--out")
+    ap.add_argument("--emit-secrets", metavar="PATH",
+                    help="write the PPPoE credential to PATH with mode 0600 and exit")
+    args = ap.parse_args()
+
+    with open(args.inventory) as fh:
+        inv = json.load(fh)
+    with open(args.raw_networkconf) as fh:
+        raw_nets = json.load(fh)
+
+    wan = next((n for n in raw_nets
+                if n.get("purpose") == "wan" and n.get("wan_username")), None)
+    if wan is None:
+        print("no WAN network with credentials found in the export", file=sys.stderr)
+        return 1
+
+    if args.emit_secrets:
+        fd = os.open(args.emit_secrets, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600)
+        with os.fdopen(fd, "w") as fh:
+            fh.write(f"WAN_PASSWORD='{wan.get('x_wan_password', '')}'\n")
+        # Re-assert the mode in case the file already existed with a wider one.
+        os.chmod(args.emit_secrets, 0o600)
+        mode = oct(os.stat(args.emit_secrets).st_mode & 0o777)
+        print(f"wrote {args.emit_secrets} (mode {mode}) for user {wan['wan_username']}",
+              file=sys.stderr)
+        return 0
+
+    lines = build_delta(inv, args.priority, wan["wan_username"], args.with_wan,
+                        args.conntrack_link)
+    text = "\n".join(lines) + "\n"
+
+    # Only a WAN-carrying delta has a credential to placeholder-substitute.
+    if args.with_wan and PLACEHOLDER not in text:
+        print("BUG: password placeholder missing from a WAN delta", file=sys.stderr)
+        return 1
+    if wan.get("x_wan_password") and wan["x_wan_password"] in text:
+        print("BUG: the WAN password leaked into the delta", file=sys.stderr)
+        return 1
+
+    n_set = sum(1 for l in lines if l.startswith("set "))
+    n_del = sum(1 for l in lines if l.startswith("delete "))
+    print(f"delta: {n_set} set, {n_del} delete, priority {args.priority}, "
+          f"{len(inv['reservations'])} reservations", file=sys.stderr)
+
+    if args.out:
+        with open(args.out, "w") as fh:
+            fh.write(text)
+        print(f"wrote {args.out}", file=sys.stderr)
+    else:
+        sys.stdout.write(text)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())

migration/vyos-unifi-switch

@@ -0,0 +1,304 @@
+#!/bin/bash
+# Switch this VyOS box between passive (USG is the gateway) and active
+# (VyOS is the gateway). Installed at /config/vyos-unifi-switch, which
+# survives image upgrades, so it can be run from a local terminal or the
+# JetKVM console with no workstation and no internet.
+#
+#   vyos-unifi-switch            report the current mode
+#   vyos-unifi-switch vyos       take over: VIPs to .1, DHCP, DNS, PPPoE, NAT
+#   vyos-unifi-switch unifi      revert; the USG can then be reconnected
+#
+# READ THIS BEFORE THE CUTOVER
+#
+# `unifi` is the escape hatch. It runs no health checks, asks no questions and
+# has nothing that can refuse. If anything at all looks wrong, run it, then
+# plug the USG back in.
+#
+# `vyos` commits with commit-confirm. If it is not confirmed -- because the
+# health checks failed, or because you lost access, or because you walked away
+# -- the box returns to the saved configuration on its own. That requires
+# `system config-management commit-confirm action reload`; without it VyOS
+# REBOOTS instead, which on a gateway is an outage rather than an undo. The
+# script refuses to run if that setting is missing.
+set -uo pipefail
+
+MODES=/config/modes
+UNIFI_BOOT="$MODES/unifi.boot"
+DELTA="$MODES/to-vyos.commands"
+SECRETS=/config/wan-secrets
+MARKER="$MODES/current-mode"
+CONFIRM_MINUTES="${CONFIRM_MINUTES:-10}"
+OPRUN=/opt/vyatta/bin/vyatta-op-cmd-wrapper
+
+say()  { printf '[switch] %s\n' "$*"; }
+warn() { printf '[switch] WARNING: %s\n' "$*" >&2; }
+die()  { printf '[switch] ERROR: %s\n' "$*" >&2; exit 1; }
+
+# Run configuration commands in a real config session. Everything the caller
+# feeds in runs between `configure` and `exit`.
+run_cfg() {
+  local script rc
+  script="$(mktemp)"
+  {
+    echo 'source /opt/vyatta/etc/functions/script-template'
+    echo 'configure'
+    cat
+    echo 'exit'
+  } > "$script"
+  vbash "$script"; rc=$?
+  rm -f "$script"
+  return $rc
+}
+
+# Two traps live in this one function, both of which produced wrong answers
+# rather than errors:
+#   1. `show configuration commands` quotes values ("action 'reload'"), so the
+#      quotes have to go before matching or every value-bearing check fails.
+#   2. `... | grep -q` under `set -o pipefail` reports FAILURE even on a match:
+#      grep exits at the first hit, the producer takes SIGPIPE, and pipefail
+#      surfaces that. Whether it triggers depends on output size, so it fails
+#      intermittently. Match against a captured string instead of a pipeline.
+cfg_has() {
+  local out
+  out="$($OPRUN show configuration commands 2>/dev/null | tr -d "'")"
+  case "$out" in *"$1"*) return 0 ;; *) return 1 ;; esac
+}
+
+# ---------------------------------------------------------------- status ----
+current_mode() {
+  # The marker records intent; the running config is the truth. Report the
+  # config, and complain if the two disagree.
+  local live="unknown"
+  if cfg_has "set service dhcp-server"; then live="vyos"; else live="unifi"; fi
+  echo "$live"
+}
+
+show_status() {
+  local live marked
+  live="$(current_mode)"
+  marked="$(cat "$MARKER" 2>/dev/null || echo "never set")"
+  echo "host:          $(hostname)"
+  echo "mode:          $live   (marker: $marked)"
+  [ "$live" != "$marked" ] && [ "$marked" != "never set" ] && \
+    warn "marker disagrees with the running config -- trust the config"
+  echo "VRRP:"
+  $OPRUN show vrrp 2>/dev/null | sed -n '3,$p' | awk '{printf "               %-9s %-12s %s\n", $1, $2, $4}'
+  echo "DHCP server:   $(systemctl is-active isc-kea-dhcp4-server 2>/dev/null)"
+  echo "DNS forwarder: $(systemctl is-active pdns-recursor 2>/dev/null)"
+  echo "WAN (pppoe0):  $(ip -4 -br addr show pppoe0 2>/dev/null | awk '{print $2, $3}' || echo 'not present')"
+  echo "default route: $(ip -4 route show default 2>/dev/null | head -1 || echo none)"
+  echo "unsaved changes: $(cfg_unsaved)"
+}
+
+cfg_unsaved() {
+  if /usr/bin/config-mgmt compare >/dev/null 2>&1; then echo "no"; else echo "possibly - check 'compare saved'"; fi
+}
+
+# ------------------------------------------------------------- preflight ----
+require_files() {
+  [ -r "$UNIFI_BOOT" ] || die "missing $UNIFI_BOOT -- capture it while the USG is still the gateway"
+  [ -s "$UNIFI_BOOT" ] || die "$UNIFI_BOOT is empty"
+}
+
+require_reload_action() {
+  cfg_has "set system config-management commit-confirm action reload" && return 0
+  die "commit-confirm action is not 'reload'. Without it an unconfirmed switch
+       REBOOTS this box instead of reverting. Fix first:
+         configure
+         set system config-management commit-confirm action reload
+         commit; save"
+}
+
+# The single worst outcome available is two devices answering on the gateway
+# address. It costs one ARP probe to make that impossible.
+# Returns 0 (success) when something IS answering on a gateway address we are
+# about to claim -- i.e. "yes, still alive, do not proceed".
+usg_still_alive() {
+  local found=0 ip dev targets
+  targets="$(grep -oE "vrrp group [a-z0-9]+ address [0-9.]+" "$DELTA" 2>/dev/null | awk '{print $NF}')"
+  if [ -z "$targets" ]; then
+    # A delta with no VIPs cannot be probed, which means the single guard
+    # against two devices sharing a gateway address is inert. Refuse by
+    # default: an unprobeable delta on the real boxes is a broken delta, and
+    # "warn and continue" would let the one failure this script exists to
+    # prevent through unnoticed. The override is for the lab only.
+    if [ "${ALLOW_NO_VIP_DELTA:-0}" = "1" ]; then
+      warn "delta claims no VIPs; proceeding because ALLOW_NO_VIP_DELTA=1 (lab only)"
+      return 1
+    fi
+    die "this delta claims no VIPs, so the gateway-address guard cannot run.
+       On the real boxes that means a broken delta. If this really is a lab
+       run, re-invoke with ALLOW_NO_VIP_DELTA=1."
+  fi
+  for ip in $targets; do
+    dev="$(ip -4 route get "$ip" 2>/dev/null | sed -n 's/.* dev \([^ ]*\).*/\1/p' | head -1)"
+    if [ -n "$dev" ] && command -v arping >/dev/null 2>&1; then
+      # ARP is the right probe: it answers even when the host filters ICMP.
+      if arping -c 2 -w 3 -f -I "$dev" "$ip" >/dev/null 2>&1; then
+        warn "something already answers ARP on $ip (via $dev)"; found=1
+      fi
+    elif ping -c 2 -W 2 "$ip" >/dev/null 2>&1; then
+      warn "something already answers ICMP on $ip"; found=1
+    fi
+  done
+  [ "$found" -eq 1 ]
+}
+
+# ------------------------------------------------------------- to unifi -----
+to_unifi() {
+  require_files
+  say "reverting to unifi mode (USG is the gateway)"
+  run_cfg <<EOF || die "load/commit failed -- the box is unchanged, use the console"
+load $UNIFI_BOOT
+commit
+save
+EOF
+  echo "unifi" > "$MARKER"
+  say "done. The USG can be reconnected."
+  say "If it was already connected during this, nothing was disturbed."
+}
+
+# -------------------------------------------------------------- to vyos -----
+health_checks() {
+  local fails=0
+  _chk() { # name, command
+    if eval "$2" >/dev/null 2>&1; then say "  ok    $1"; else say "  FAIL  $1"; fails=$((fails+1)); fi
+  }
+  _chk "kea (DHCP) is running"      "systemctl is-active --quiet isc-kea-dhcp4-server"
+  _chk "DNS forwarder is running"   "systemctl is-active --quiet pdns-recursor"
+
+  # Only assert on the WAN if this delta actually brings one up. A delta with
+  # no PPPoE stanza is a lab/partial delta, and failing it on a missing
+  # pppoe0 would make the script untestable anywhere but the live cutover.
+  # Announced loudly, because a quietly skipped check is worse than no check.
+  # A box whose delta holds its WAN interfaces DOWN is the backup: it has no
+  # route out by design, and demanding one reverts a perfectly correct config.
+  # This tore down vyos002 on the first successful cutover -- vyos001 went live
+  # and its backup was judged unhealthy for lacking the WAN it is deliberately
+  # not carrying. Same mistake as requiring the failover line: checks that do
+  # not apply to the box being checked.
+  if grep -qE "^set interfaces (pppoe pppoe0|bonding bond0 vif 53) disable$" "$DELTA"; then
+    say "  note  this box holds its WAN down (backup); skipping WAN checks"
+  elif grep -qE "^set interfaces (pppoe|bonding bond0 vif 5)" "$DELTA"; then
+    # What matters is that SOME WAN works, not that every WAN works.
+    #
+    # This reverted a cutover that had genuinely succeeded. The 10 gig line came
+    # up on bond0.53 and the cloned MAC was handed the same public address the
+    # USG had (87.192.101.48); kea was serving real LAN clients at the same
+    # moment. The only failure was pppoe0 -- the Vodafone FAILOVER line -- and
+    # requiring it undid a working gateway.
+    #
+    # Written as [ -n "$(...)" ] rather than `... | grep -q` for the pipefail
+    # reason above: a pipeline ending in grep -q cannot be trusted here.
+    _chk "a default route exists"   '[ -n "$(ip -4 route show default)" ]'
+    _chk "internet reachable"       "ping -c2 -W3 8.8.8.8"
+    _chk "DNS resolves through us"  "getent hosts vyos.net"
+
+    # Informational only: report each WAN, fail on neither. A failover line
+    # being down is worth seeing, not worth reverting for.
+    for _w in pppoe0 bond0.53; do
+      if [ -n "$(ip -4 -br addr show "$_w" 2>/dev/null | awk '{print $3}')" ]; then
+        say "  ok    WAN $_w has an address (informational)"
+      else
+        say "  note  WAN $_w has no address (informational, not fatal)"
+      fi
+    done
+  else
+    warn "this delta configures no WAN -- skipping all WAN health checks."
+    warn "That is expected in the lab and WRONG for the real cutover."
+  fi
+  return $fails
+}
+
+to_vyos() {
+  require_files
+  require_reload_action
+  [ -r "$DELTA" ] || die "missing $DELTA"
+
+  if usg_still_alive; then
+    die "refusing: something is still answering on a gateway address.
+       Disconnect the USG first. Two devices on the same gateway IP is the
+       one failure this script exists to prevent."
+  fi
+
+  local pw="" tmp
+  if [ -r "$SECRETS" ]; then
+    # shellcheck disable=SC1090
+    . "$SECRETS"; pw="${WAN_PASSWORD:-}"
+  fi
+  [ -n "$pw" ] || warn "no WAN_PASSWORD in $SECRETS -- PPPoE will not authenticate"
+
+  tmp="$(mktemp)"; chmod 600 "$tmp"
+  sed "s|@@WAN_PASSWORD@@|${pw}|g" "$DELTA" | grep -vE '^\s*(#|$)' > "$tmp"
+
+  say "switching to vyos mode (this box becomes the gateway)"
+  say "commit-confirm: ${CONFIRM_MINUTES} min to confirm, else it reverts itself"
+
+  # commit-confirm is TWO steps, and doing only the first commits nothing:
+  # `config-mgmt commit_confirm` arms the revert timer, then a normal `commit`
+  # applies the candidate config. The interactive prompt lives in the first
+  # step, which is why it is invoked directly with -y instead of via the
+  # `commit-confirm` alias. IN_COMMIT_CONFIRM is what the real CLI sets, and
+  # the commit hooks look at it.
+  if ! run_cfg < <(printf 'load %s\n' "$UNIFI_BOOT"; cat "$tmp";
+                   printf 'sudo sg vyattacfg "/usr/bin/config-mgmt commit_confirm -y -t=%s"\n' "$CONFIRM_MINUTES";
+                   printf 'export IN_COMMIT_CONFIRM=t\ncommit\nunset IN_COMMIT_CONFIRM\n'); then
+    rm -f "$tmp"
+    die "commit-confirm failed. Nothing was applied; the box is still in its
+       previous mode. Run '$0 unifi' if you are unsure."
+  fi
+  rm -f "$tmp"
+
+  # Poll, do not sample once.
+  #
+  # A cutover attempt failed here on a fixed 25s wait. That is far too short for
+  # a WAN: PPPoE is PADI/PADO/PADR/PADS then LCP, auth and IPCP, routinely 15-30s
+  # by itself, and both lines had just been released by the USG seconds earlier.
+  # ISPs commonly hold the previous session and MAC binding for minutes before
+  # leasing to the "same" CPE again -- which is precisely what a cloned MAC looks
+  # like to them. One sample at 25s reported a healthy setup as broken and
+  # reverted it.
+  #
+  # There is still a deadline, because commit-confirm is running: stop well
+  # before it so the decision is ours rather than the timer's.
+  local budget="${HEALTH_BUDGET:-180}" waited=0 step=15
+  say "committed. Polling health for up to ${budget}s (commit-confirm has ${CONFIRM_MINUTES} min)..."
+  while :; do
+    sleep "$step"; waited=$(( waited + step ))
+    if health_checks >/dev/null 2>&1; then
+      say "healthy after ${waited}s"
+      break
+    fi
+    if [ "$waited" -ge "$budget" ]; then
+      say "still unhealthy after ${waited}s -- final check:"
+      break
+    fi
+    say "  not healthy yet at ${waited}s, still waiting..."
+  done
+
+  say "health checks:"
+  if health_checks; then
+    say "all checks passed -- confirming"
+    /usr/bin/config-mgmt confirm >/dev/null 2>&1 || die "confirm failed; it will revert on its own shortly"
+    run_cfg <<'EOF' || warn "save failed -- config is live but will not survive a reboot"
+save
+EOF
+    echo "vyos" > "$MARKER"
+    say "vyos mode is live and saved."
+  else
+    warn "health checks FAILED -- reverting now rather than waiting out the timer"
+    /usr/bin/config-mgmt revert_soft >/dev/null 2>&1 \
+      || warn "revert_soft failed; the commit-confirm timer will still fire within ${CONFIRM_MINUTES} min"
+    echo "unifi" > "$MARKER"
+    die "reverted to the previous configuration. Reconnect the USG.
+       Check: ip addr show pppoe0; journalctl -u pppd; $0 status"
+  fi
+}
+
+# ----------------------------------------------------------------- main -----
+case "${1:-status}" in
+  vyos)   to_vyos ;;
+  unifi)  to_unifi ;;
+  status) show_status ;;
+  *)      echo "usage: $(basename "$0") [vyos|unifi|status]" >&2; exit 2 ;;
+esac