Just recording my own FUBAR and fix for the community.
After updating to OPNsense 24.1.8-amd64 this morning, the default route would not come up. Trying 'route add default [gw ip]' just gave "route: writing to routing socket: Network is unreachable". 'netstat -rn' listed igb[1..5] but not igb0. The GUI did helpfully provide a clue; /ui/routing/configuration showed the WAN "Status" as yellow with a "mis-configured IP" hint.
Issue was, IP configured for the igb0 WAN interface had a /32 netmask. This was likely mis-configured while thrashing at a NAT configuration during the initial install. (But also, that mis-config has worked since August, 2020.) The fix was simply setting this to /24. The default route then autoloaded.
Hi,
Thanks for your feedback. I've heard the same on Reddit a few times and I think it's due to this fix in 23.1.8:
https://github.com/opnsense/core/commit/a683004fba
Which previously would actually set the "far gateway" option for such setups and fixed the misconfiguration by accident. Unfortunately this was causing other problems with VPN tunnels being defunct or throwing spurious system error message for example.
Cheers,
Franco