VLAN 2 IPv6 applied to production: RA proven, MAC reservations do NOT match

The unattended window's W1/W2. Both routers now carry the VLAN 2 IPv6 config
(addresses ::1/::2, RA with managed-flag + no-autonomous-flag + link-mtu 1472,
DHCPv6 reservations for all five nodes), applied via migration/vlan2-v6-apply
with a vlan2-v6-watchdog armed on both routers throughout. IPv4 untouched:
internet up, 6 MASTER / 6 BACKUP, 5/5 nodes Ready, watchdogs quiet.

default-lifetime 0 on purpose -- addressing without egress. Turning on v6
egress moves image pulls onto a tunnel of unmeasured throughput, and the person
who would notice is away. One line to flip when attended.

THE WINDOW'S QUESTION IS ANSWERED, HALF YES, HALF NO:

YES: NetworkManager follows the managed flag. worker0 logged
  dhcp6 (eno1): activation: beginning transaction
minutes after the RA appeared. "ipv6.method=auto will do DHCPv6" is now
evidence, not inference.

NO: the reservations never match. Every packet kea logs is [no hwaddr info] --
the clients identify with DUID-UUID (and one DUID-LLT), kea derives no MAC from
any of them, so hw-address reservations cannot match and no node got its
reserved address. VyOS accepting `static-mapping mac` renders valid kea config
that simply never matches these clients. The "one source of truth with IPv4"
addressing scheme does not survive contact with DHCPv6; options (DUID keys, kea
mac-sources, dynamic range + discovery, or SLAAC) are written up in
migration/window-evidence/2026-09-06-dhcpv6.txt for an attended decision.

FOUND LIVE AND FIXED IN THE SAME WINDOW: `service dhcpv6-server` with no
listen-interface renders kea6 with interfaces: ["*"] -- a DHCPv6 server on
EVERY VLAN. kea was answering an unrelated device on bond0.10 within seconds of
the first apply. Same family as the kea IPv4 cross-VLAN bug (ISC #1117). Now
pinned to bond0.2 on both routers.

Also in this commit, three self-inflicted script bugs found by their own
failures: log() wrote progress lines into the captured config stream (VyOS
rejected each as "Invalid command", leaving the two routers correct but NOT
identical); "Invalid command" was missing from the failure patterns so that run
reported success; and the MAC lookup matched its own freshly-created v6
reservations on the second run, returning doubled MACs. All three fixed, both
routers converged and diffed identical.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DMVzWZgiKW2wquf5z8S1yH

migration/window-evidence/2026-09-06-dhcpv6.txt

@@ -0,0 +1,56 @@
+=== W2: does a production node take a DHCPv6 reservation? ===
+Window of 2026-09-06, operator offline.
+
+SHORT ANSWER: the RA half works; the RESERVATION half does not, and the reason
+is structural rather than a misconfiguration.
+
+WHAT WORKS
+  - RA is emitted on bond0.2 with AdvManagedFlag on, AdvAutonomous off,
+    AdvLinkMTU 1472, AdvDefaultLifetime 0 (deliberately not a default router).
+  - NetworkManager on worker0 SAW it and acted: 
+      dhcp6 (eno1): activation: beginning transaction (timeout in 45 seconds)
+    So "ipv6.method=auto follows the managed flag" is now EVIDENCE, not
+    inference. That was the open question this window set out to close.
+  - kea-dhcp6 runs on both routers and receives SOLICITs on bond0.2.
+
+WHAT DOES NOT WORK, AND WHY
+  Every DHCPv6 packet kea logs is annotated [no hwaddr info]:
+
+    duid=[00:04:69:d9:30:64:c3:4e:...]  [no hwaddr info]   <- DUID-UUID (type 4)
+    duid=[00:04:25:11:e0:0a:7b:c4:...]  [no hwaddr info]   <- DUID-UUID
+    duid=[00:01:00:01:31:78:0a:ae:...]  [no hwaddr info]   <- DUID-LLT (type 1)
+
+  DHCPv6 identifies a client by DUID, not by MAC. kea can sometimes DERIVE a MAC
+  (its mac-sources machinery), but here it derives nothing -- including from a
+  DUID-LLT, which does embed one. So `hw-address` reservations cannot match, and
+  a node that solicits gets no reserved address.
+
+  VyOS accepting `static-mapping <name> mac` is therefore necessary but NOT
+  sufficient: it renders valid kea config ("hw-address": "78:55:36:08:28:fb",
+  confirmed in /run/kea/kea-dhcp6.conf) that simply never matches these clients.
+  The plan's assumption -- "reservations keyed on MAC, one source of truth with
+  IPv4" -- does not survive contact with DHCPv6.
+
+OPTIONS, none free, for an attended session:
+  a) Key reservations on DUID (VyOS static-mapping supports `duid`). Works, but a
+     DUID is client-generated: it is a SECOND source of truth, it must be
+     harvested per node, and it changes if a node is rebuilt -- which is exactly
+     the "out of the box for new nodes" property we were trying to preserve.
+  b) Set kea `mac-sources` explicitly and see whether any method recovers a MAC
+     from these clients. Cheap to try; may simply not work for DUID-UUID.
+  c) Drop reservations: hand out a dynamic range and have labctl DISCOVER the
+     node's address rather than predict it. The k3s preflight (914135c) already
+     refuses to write a node-ip the node does not hold, so discovery is safe --
+     but the address is then not knowable before the node boots.
+  d) SLAAC with no-autonomous cleared, and accept EUI-64 addresses. Stable per
+     NIC and needs no server state at all, but the address is not ours to choose.
+
+A SECOND FINDING, unrelated and worse if unnoticed
+  `service dhcpv6-server` with no listen-interface renders kea6 with
+  interfaces: [ "*" ] -- a DHCPv6 server on EVERY VLAN. Observed live: kea began
+  answering SOLICIT/REQUEST from an unrelated device on bond0.10 (LoT) within
+  seconds of the first apply. Same family as the kea IPv4 cross-VLAN bug (ISC
+  #1117) this estate already fought. Fixed by pinning
+  `set service dhcpv6-server listen-interface bond0.2` plus a subnet-level
+  `interface bond0.2`; both routers now render interfaces: ["bond0.2"].
+