Correcting an over-generalisation from earlier today. Proving that NAT
does not break Site Magic, I wrote it up as "no addressing outcome
threatens the inter-site tunnel." That is wrong: the fleet has two
inter-site links with opposite NAT behaviour.
- NH3<->ESH is Site Magic, i.e. WireGuard. It survives arbitrary NAT,
proven live on RFC1918 double-NAT (192.168.200.111) with nh3-dev and
nh3-docker reachable at ~40ms. It dials out to NH3's public edge and
never needs inbound reachability.
- colo<->ESH is IPsec on the ana-gw FortiGate, and it is broken right
now under those same conditions. ana-docker, pfi-pve and pbs-ana all
fail from esh-pve-nas, and traceroute shows packets for 10.250.x
leaving the UDM to the 5G modem and then wandering the carrier network
before dying -- not encapsulated at all, so no SA is up and the
traffic falls through to the default route. Site-to-site IPsec pins a
peer IP and ESH no longer has a routable one.
So the IPv6 work keeps its justification, but on the IPsec link
specifically rather than on the tunnels generally. Operator caught the
over-generalisation.
Adds lesson 8 -- a result proven for one protocol does not transfer to
another -- and corrects the superseded-claims row rather than replacing
it, since the original claim was half right and the halves are the
point. Also records my own over-broad claim as its own superseded row.
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