VOICE: IOS SIP Trunk 403 Forbidden error?

I spent a few hours on this one. Here is the situation:

Cisco 2621XM has a SIP trunk setup between itself and an online SIP trunk provider called voipfone.co.uk. The trunk is up and established:

Screen shot 2011-10-20 at 17.30.24

I cal make calls outbound to their ECHO test number on 152 and their COURTESY number 155. I can also take incoming calls to my SIP number 057XXXXXXXX. This all looks good. What I can't do however is call anything outbound on any number other than those test numbers. After a few hours I figured this had to be something to do with authentication. Basically my reasoning was that maybe those service numbers (152/155) might just be globally allowed (FREE to use) numbers. Once I try to access a paid number I'll need to be authenticated.

So I quickly ran up a debug for the SIP call.

Screen shot 2011-10-20 at 17.19.49

After making a new test call to an external number I picked up on the dreaded SIP/2.0 403 Forbidden error in the debug logs:

Screen shot 2011-10-20 at 17.20.05

So there it was, my authentication error, but how do I fix it? I looked under the sip-ua configuration and found my credential and authentication statements. I removed them and put them back again, still not working. Clearly this was something else. After using the context help I found the 'calling-info' command. This command had a few arguments that looked interesting and one of them was specifically for calls gong to and from the PSTN...so I drilled into it.

Screen shot 2011-10-20 at 17.24.13

After entering this command my trunk started to allow outbound calls. Also the debug showed that the 403 Forbidden had gone away.

Great stuff!

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