Troubleshooting SIP Trunk Instability Issue Between CUCM

[edmarcarvalho29177]

"I kindly request your assistance in resolving this incident that has been causing instability between two SIP trunks, one on CUCM 9.x and the other on CUCM 6.1x. The current issue is as follows: whenever an extension attempts to make a call via the SIP trunk, after one side answers, the connection is abruptly terminated.

I have collected the logs and have identified the following error:

76498951.002 |14:53:36.563 |AppInfo |SIPTcp - wait_SdlReadRsp: Incoming SIP TCP message from 10.5.32.144 on port 42157 index 133712 with 496 bytes:
[5409214,NET]
BYE sip:42108@10.7.68.11:5060;transport=tcp SIP/2.0
Reason: Q.850;cause=47
Date: Tue, 03 Oct 2023 13:42:19 GMT
From: "Luisa Carvalho" <sip:50277@10.5.32.144>;tag=d9698221-4943-4406-85ff-42da9148fa32-31169890
Content-Length: 0
User-Agent: Cisco-CUCM6.1
To: <sip:42108@10.7.68.11>;tag=1536245~e1f43248-a6e3-4ddd-a64c-2b7a2f809d73-256912708
Call-ID: aabcf500-51c11a3b-297f-9020050a@10.5.32.144
Via: SIP/2.0/TCP 10.5.32.144:5060;branch=z9hG4bK4d6b695a1f5b
CSeq: 103 BYE
Max-Forwards: 70

[Maren Mahoney]

The disconnect cause code Q.850:Cause=47 most often indicates failure to negotiate a common codec. And the behavior of a call (dial, ring, immediate disconnect on pickup) is consistent with a codec-mismatch issue.

Check the Region settings on the device pools of the originating phone, outgoing trunk on the originating leg - and then the Region on the device pools of the receiving trunk and the receiving phone. 

You can also look at the SDP negotiation in the SIP Message exchange to see what is being sent/requested by each component.

Maren

[Roger Kallberg]

Apart from what @Maren Mahoney wrote you should be aware of that both of your versions of CM has passed all support. Version 6 is from way back about 14-15 years and version 9 is also many years ago since it was released. You would be advised to upgrade to something more current.