Working with SIP Trunk and SFB CCE

Frequent Contributor

Recently I deployed a Sonus SFB CCE with a new SIP Trunk instead of a traditional ISDN line.

All went fine, but a stream of PSTN calls related issue sprung out. I did follow the same setup steps that I had successfully done with other (Sonus/Audiocodes) SFB CCE deployments apart from the fact that this time I am using a SIP Trunk.

Working with SIP Trunk is pretty much different from ISDN line we accustomed to.

I’ll go on straight to core issues that some of you would encounter when you do the same (Sonus/Audiocodes) CCE deployment with a SIP trunk line.

It’s important and interesting to take note that I didn’t face this issue and didn’t have to make any changes with traditional ISDN line like I did  with the SIP Trunk. So, it is apparent that the issues faced and respective solutions are only applicable for SIP trunk line or specific SIP provider. 


When a SFB Online user (Enterprise Voice enabled and a telephone number assigned) makes an outgoing calls, and it failed – cannot make a successful outgoing call(s).

All incoming calls are working fine.

Outgoing Call(s) Failure Symptom(s)

  • Cannot make outgoing call(s).

  • You will hear an automated voice message from your SIP provider, something like “your call is restricted” when you made outgoing call(s).

  • Just simply outgoing call(s) failed.


Root Cause:
The root cause of the issue is that the SIP provider is in fact EXPECTING a certain SIP message format from the SIP MESSAGE sent from the Voice Gateway (Sonus, AudioCodes, etc), specifically INVITE, FROM and P-ASSERTED IDENTITY.





Detailed solution is mentioned here at my TechNet page: 

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