nh3-dev sits on the NH3 LAN and reaches every site through its own default
gateway; RouteAll was already false, so it never used the tunnel for routing.
Membership bought a 100.64.0.4 address nothing referenced -- grep across the
repo and ~/development found only docs and memory hits.
It also cost something concrete. A host running Tailscale installs
-A ts-input -s 100.64.0.0/10 ! -i tailscale0 -j DROP, and because the fleet's
subnet routers preserve source rather than masquerading RFC1918, a mesh client's
packet reached nh3-dev's ens18 still sourced 100.64.x and was dropped silently.
That is why nh3-dev.nh3.internal failed from the mesh while every NH3 host that
does not run Tailscale worked, and it needed a -d 10.100.10.50/32 -j MASQUERADE
exception on nh3-scale to paper over. Retiring the membership removed the
anti-spoof rule, so the exception went with it -- mesh-exit-masq.sh is back to
the two rules it had before yesterday.
Verified after: nh3-dev reachable at 10.100.10.50 from ESH, Anaheim, FV, Irvine
and NH3, and reaching all four sites plus the internet itself. fv-ml1
unaffected.
The mesh is now six nodes and every one has a job: three site routers,
vb-gateway, irv-ml1 (Irvine's own router, no separate scale node), and the
operator's MacBook Air. Nothing is enrolled just in case.
FV could not reach any site but Anaheim. The cause was a single outbound-NAT
rule on the FV gateway, added 2026-09-13 and scoped to Anaheim only --
docs/runbooks/fv-to-ana-nat.md says so in as many words: "Other remote sites
remain outside this fix's scope." Three mirrors added, same interface and
source, only the destination differing: 10.100.0.0/16, 10.0.0.0/16 and
10.6.110.0/24.
After: fv-ml1 reaches NH3, ESH, Anaheim, Irvine, the mesh and the internet.
Regression sweep clean across nh3-dev, nh3-docker and esh-docker-vm.
The runbook now records what the failure looks like, because it presents as a
routing or Tailscale fault and is neither. fv-ml1 reached mesh addresses
perfectly and LAN addresses not at all; the FV firewall log showed the outbound
passing with src=10.251.50.54 and no reply returning; temporary counting rules
proved nh3-scale received 5 packets and sent 4 replies; both peers' AllowedIPs
were correct. The discriminator that settles it is that every other site pair
works -- nh3-docker to esh/ana/FV and esh-docker-vm to FV all succeed -- so a
general subnet-to-subnet limitation is ruled out and only outbound SNAT is
left.
Also reverts the remote-site MASQUERADE rules added to nh3-scale earlier on the
asymmetric-return theory. They fired but were not the fix, so they are removed
rather than left to accumulate as NAT that achieves nothing.
Applied via source_nat/add_rule + apply with a pre-change config backup taken
first. Source scope is still fv-ml1's /32, so a second FV host will hit this
again -- flagged in the runbook.
WATCHDOG (done, proven). fv-mesh-watchdog probes two independent anchors every
minute and, after 5 consecutive failures, puts Tailscale back to known-good:
accept-routes off, re-up against headscale with a stored key. It touches
nothing else — a watchdog with a wide remit is a second way to lose the box.
Two anchors that cannot share a failure mode: a plain-internet one and a
mesh-only one. If BOTH fail the site uplink is down, Tailscale cannot fix that,
and it deliberately does nothing — thrashing tailscaled during an ISP outage
turns a wait into an incident. Disable file at /etc/fv-watchdog.disable for
planned work.
Proven by positive control, not assumed: counter incremented 1..4 without
acting, fired the restore at 5 (tailscale up ran, tailscaled restarted), and
reset to 0 once the real anchor returned. fv-ml1 stayed reachable throughout.
This exists because a on fv-ml1 black-holed it
from its own LAN earlier the same day: it accepted 10.251.0.0/16 from the
gateway — its OWN subnet — and routed the local network through the tunnel.
FV CROSS-SITE ROUTING (partial). Two changes landed, the path is still broken:
1. acceptSubnetRoutes 0 -> 1 on the FV gateway's tailscale plugin, via
settings/set + service/reconfigure (the documented apply, not a reboot).
The GATEWAY now has 10.0/16, 10.100/16 and 10.250/16 in its routing table
and reaches NH3 and ESH itself. It could not before.
2. Remote-site MASQUERADE rules on nh3-scale. The existing jump matched only
-s 100.64.0.0/10, so traffic from another site's LAN never entered
MESH-EXIT and kept its original source; an NH3 host then replied via its
own LAN router instead of back through nh3-scale, making the path
asymmetric. The rule is confirmed firing (counter increments on FV
traffic) but does not complete the path.
Still failing: fv-ml1 -> NH3/ESH LAN addresses. Mesh addresses work perfectly
from fv-ml1 (100.64.0.1, 100.64.0.4), Anaheim works over the metro link, and
the FV firewall log shows the outbound passing on tailscale0 with
src=10.251.50.54 and no reply ever returning. The remaining gap is forwarded
FV-LAN traffic specifically, not the gateway's own.
Full regression sweep clean: nh3-dev, ana-docker and esh-docker-vm all reach
all four sites plus the internet.
One rule on nh3-scale (CT 107): -d 10.100.10.50/32 -j MASQUERADE, above the
RFC1918 RETURNs in /usr/local/sbin/mesh-exit-masq.sh, so it survives a reboot
rather than living only in the running ruleset.
Cause. A host that runs Tailscale installs -A ts-input -s 100.64.0.0/10
! -i tailscale0 -j DROP. The fleet's subnet routers run NoSNAT: true with
RFC1918 explicitly exempted from masquerade — deliberate source preservation,
and a departure from Tailscale's own --snat-subnet-routes=true default — so a
mesh client's packet reached nh3-dev's ens18 still sourced 100.64.x and died
at the anti-spoof rule. Every NH3 host that does not run Tailscale was
unaffected, which is why this read as a DNS or routing fault rather than a
policy one. Masquerading just this destination makes it behave like every
other host and leaves source preservation absolute elsewhere.
Verified before and after against 13 targets from nh3-dev and 9 from the
MacBook Air, and again after restarting the service so the chain was rebuilt
from the script rather than from the manual insert. nh3-dev.nh3.internal now
resolves and connects from the mesh, ssh and the Booth port included, with no
script changes anywhere.
Records the failed approach prominently, because it is the attractive one:
advertising 10.100.10.50/32 from nh3-dev itself black-holed it from ESH,
Anaheim, FV and Irvine. ip rule there puts lookup 52 at priority 5270 ahead of
main at 32766, and becoming a subnet router let table 52 capture cross-site
traffic the node has no accepted route for. Its own LAN and the internet kept
working throughout, so a single-host check confirms a break it cannot see.
vh