Last week I noticed one of our lines wasn't accepting calls (the one starting with 950). Outgoing calls on both lines are fine (both on Asterisk).
I started playing around with settings in Asterisk and my firewall (ALG, NAT and so on) but have not managed to find nor fix the issue. I must stress that I started going through everything *after* the fault, however the server this was on did suffer from a full disc a few days earlier, although that was freed up and the server then restarted. I don't know if the two issues are coincidental or not. We may not have noticed the issue for a couple of days, or it may not have happened for a couple of days.
We have two trunk lines. The (ported) one starting with 940 works fine. The other one starting with 950 can place but not receive calls, they go instantly to the voice portal.
"sip show registry" shows both trunks as registered.
endeavour*CLI> sip show registry
Host Username Refresh State Reg.Time
pan.wxnz.net:5060 9940XXXX 285 Registered Sat, 23 Apr 2011 13:07:57
pan.wxnz.net:5060 9950XXXX 285 Registered Sat, 23 Apr 2011 13:07:57
Any ideas as to what to check next? A few months ago the same problem was caused by a corrupt SIP registration, but this time I waited several days for that to clear before doing anything.