3CX with Comcast SIP, dropped calls

[JPElectron]

Having a problem where Comcast has checked the equipment and says everything is fine, yet we're still getting dropped calls for no explainable reason. Internal calls work fine.

For those unfamiliar, the way Comcast works is they put an Adtran box inside your network on the LAN, and you connect to that as a VoIP provider in 3CX. Anyone else have experience with this, I followed the Comcast provided setup steps exactly, and everything works great, except the occasional dropped calls.

User's phone is a Cisco 7940, which seems OK, tried replacing with a Snom, noticed no difference.

This happened to be an outbound call, from the logs...

24-Jun-2015 12:21:05.147 Leg L:124.2[Line:10000>>1815218****] is terminated: Cause: BYE from PBX
24-Jun-2015 12:21:05.147 [CM503008]: Call(C:124): Call is terminated
24-Jun-2015 12:21:05.141 Leg L:124.1[Extn] is terminated: Cause: BYE from 172.17.122.91:50631
24-Jun-2015 12:20:40.015 Currently active calls - 1: [124]
24-Jun-2015 12:20:08.004 Currently active calls - 1: [124]
24-Jun-2015 12:19:58.570 [CM503007]: Call(C:124): Line:10000>>1815218**** has joined, contact <sip:815639****@172.17.122.25:5060>
24-Jun-2015 12:19:58.570 [CM503007]: Call(C:124): Extn:507 has joined, contact <sip:[email protected]:5060>
24-Jun-2015 12:19:58.564 L:124.2[Line:10000>>1815218****] has joined to L:124.1[Extn]
24-Jun-2015 12:19:42.547 [CM505003]: Provider:[Comcast] Device info: Device Not Identified: User Agent not matched; Capabilities:[reinvite, replaces, able-no-sdp, recvonly] UserAgent: [ADTRAN_NetVanta_3430/R11.3.0.V (s00a0c8ae3f5a)] PBX contact: [sip:815639****@172.17.122.27:5060]
24-Jun-2015 12:19:41.270 [CM503025]: Call(C:124): Calling T:Line:10000>>1815218****@[Dev:sip:[email protected]:5060] for L:124.1[Extn]
24-Jun-2015 12:19:41.249 [CM503027]: Call(C:124): From: Extn:507 ("Todd ****" <sip:[email protected]:5060>) to T:Line:10000>>1815218****@[Dev:sip:815639****@172.17.122.25:5060]
24-Jun-2015 12:19:41.249 [CM503004]: Call(C:124): Route 1: from L:124.1[Extn] to T:Line:10000>>1815218****@[Dev:sip:815639****@172.17.122.25:5060]
24-Jun-2015 12:19:41.249 Line limit check: Current # of calls for line Lc:10000(@Comcast[<sip:[email protected]:5060>]) is 0; limit is 6
24-Jun-2015 12:19:41.249 Call(C:124): Call from Extn:507 to 1815218**** matches outbound rule 'Rule for Comcast'
24-Jun-2015 12:19:41.248 [CM503001]: Call(C:124): Incoming call from Extn:507 to <sip:1815218****@172.17.122.28:5060>

 

[leejor]

If I had to guess, and at this point that's all it would be, I would say that an ACK (or other SIP message) is not getting through, at times. You might try using Wireshark as it would show all messages, or at least what was being sent, or not, as the case may be.
Intermittent problems are the worst to try to troubleshoot.