Phone stops receiving calls after 5 mins

Hello all - I have been having an issue where my phones (Cisco 7960 and Sipura SPA-841) only receive calls for about 5 mins after they are turned on, then they must be rebooted to start receiving again. They make outgoing calls with no problem…

I am pretty sure it is an issue with my Asterisk server being that it is happening with both phones.

Any ideas would be greatly appreciated!


Asterisk DEBUG info

Sip read:
SIP/2.0 400 Bad Request
Via: SIP/2.0/UDP;branch=z9hG4bK2227f58f;rport
From: “Unknown”;tag=as6131fdc9
To: sip:101@64.9.x.x:5060
Date: Tue, 29 Nov 2005 09:45:44 GMT
Warning: 399 Bad Request - 'Invalid SDP information’
CSeq: 102 NOTIFY
Content-Length: 0

if there is NAT involved it may involve lapsed nat mappings. try turning on qualify=yes in sip.conf. Alternatively, if they are behind the same NAT or are on the local LAN, make sure the phones arent configured for STUN or have external ip address defined

Great, I have enabled qualify=yes and so far, so good! I will let you know if it continues to work.

The phones are behind a cable modem at a remote site and connect to our PBX via our T-1.