So I have a super random fault with a SIP trunk. It's only cropping up very randomly and been really hard to get any decent info..
But I finally managed to make it fault with a packet capture running. My only annoyance was I did the capture off the PPPoE interface and not LAN bridge so I don't know what actually got to the LAN.
So the PBX receives an INVITE from the SIP proxy, but then right after that, the router "replies" with an "ICMP 590 Destination unreachable (port unreachable)"
I kind of take that for what it is, the port was unreachable. My thought process goes there was no state in the sessions table that matched so it couldn't get through the NAT.
Do people agree? Maybe just pull my registration timer (currently 120) and notfy timer (currently 30s) right down? Increase the UDP timeout (currently 1m) in the sessions table?
My main annoyance is this is my standard router config and a standard PBX config in use on 300+ other sites. Also a VERY basic network.