SIP CALLS DROPPED TO CUCM VIA VOICE GATEWAY (SIP/2.0 503 Service Unavailable Reason: Q.850;cause=47)

[DavidW]

I have set up a SIP trunk from my  3rd party PBX to my IOS 12 voice gateway which in turn forwards calls to CUCM. Calls from phones registered on CUCM are working fine, however calls from PBX to CUCM via the router do not go through. The phone keeps beeping even after answering.

From the debugs, I get the below output.

SIP/2.0 503 Service Unavailable
Via: SIP/2.0/UDP 192.168.12.253:5060;rport;branch=z9hG4bKPjdbe4fcd3-6b6c-49e7-b583-8c6808f033d7
From: "Test IT" <sip:6002@192.168.12.253>;tag=8ba4a1ac-5998-4369-b511-740abf1d6ebc
To: <sip:2632@192.168.12.53>;tag=CC93B5B8-96E
Date: Fri, 05 Jul 2019 05:37:38 GMT
Call-ID: f4a76afc-ba2b-494c-b199-1d017d099c61
Server: Cisco-SIPGateway/IOS-12.x
CSeq: 6212 INVITE
Allow-Events: telephone-event
Reason: Q.850;cause=47
Content-Length: 0

Any way this can be resolved? I have not been able to get a working solution on the forums.

Attached is a capture of the stream.

[Maren Mahoney]

A Reason: Q.850;cause=47 disconnect error usually indicates a codec negotiation problem. Please post a sanitized copy of your router's configuration and a debug of a failed call. We can take a look and help you troubleshoot.

Maren

[DavidW]

Thanks for your response.

Attached are the debugs and running config

[DavidW]

Enabling inbound faststart on CUCM solved my problem

[Maren Mahoney]

I'm glad you figured it out!

I apologize for this falling off my radar. I had downloaded your traces and didn't manage to do the analysis I hoped to.

Maren