SIP TRUNK (incoming calls not working, outbound OK)

Unanswered Question
Oct 28th, 2008


When configuring a Sip trunk with cucm 5.1.2(3000) to an operator sip gateway outbound calls work correctly.

When trying to get an inbound call, the gateway receives the following from CUCM:


SIP/2.0 503 Service Unavailable

Warning: 399 "Routing Failed:..."


And a fast busy signal is given to the caller.

What does this message means, and how can i debug and solve the problem.

I'm really stuck.



I have this problem too.
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Brandon Buffin Tue, 10/28/2008 - 05:33

Make sure your SIP trunk has a Calling Search Space for inbound calls that can reach the required DN, translation pattern, etc.

Hope this helps.


metalium2007 Tue, 10/28/2008 - 05:47

Dear friend,

Ive checked that. And it should reach the DN. I don't understand what can be my problem since the message routing failed is not explicit.



Brandon Buffin Tue, 10/28/2008 - 05:59

What do you have for "Significant Digits" for incoming calls? What number is being sent by the providor? Does this number and the significant digits that you are matching match a DN?


metalium2007 Tue, 10/28/2008 - 06:37

- 9 significant digits

Then they are transformed into a DN (5 digits) via translation pattern.

(checked the transformation dialing from another phone and it works)



Brandon Buffin Tue, 10/28/2008 - 08:09

Be sure the Calling Search Space assigned to the SIP trunk can reach the Partition assigned to the translation pattern and the Calling Search Space assigned to the translation pattern can reach the Partition assigned to the DN.


metalium2007 Tue, 10/28/2008 - 08:21

Ok, im 99% sure of that, but ill check anyway.

Any service or service parameter that i should use? Anything related with tcp and udp on sip security profile? i'm using the default.



metalium2007 Thu, 10/30/2008 - 13:40

Ok. Problem solved.

Provider provided sip gateway local address and didnt have nat to their public address.

After establishing SIP trunk between CUCM cluster and public sip address, calls work incoming and outgoing.

Thanks for suggestions,




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