Solved Nexmo SIP Trunk Suddenly Responding with 403

[kelsallp]

A Nexmo SIP Trunk, which as been configured as per the guide, and has been working for 2 years without problem, has suddenly stopped passing calls to 3CX. When I view the logs on Nexmo, I can see the call was rejected with a 403 code.

Any ideas why this might be?

 

[kelsallp]

A response from Vonage:

The Vonage platform injects code 403 into the CDR when a call is rejected by a customer SIP endpoint.

The SIP 407 response is generated by the 3CX platform, and this essentially rejects the call, that is when we insert 403 into the final CDR.

To confirm, Vonage is sending the call correctly to the 3CX endpoint. However, the 3CX server is responding to the INVITE incorrectly with a 407 response. 407 responses indicate authentication is required and this is not supported.

If you do not maintain the 3XC SIP endpoint, I would suggest that you contact 3CX asking them to ensure they do not challenge Vonage SIP INVITEs to your sip:[email protected] endpoint (xxxs from me). This will resolve the problem.

Strange that this is suddenly happening.

 

[kelsallp]

Deleted the SIP trunk, re-set up the trunk (same values), now works :-(

 

[YiannisH_3CX]

Hello @kelsallp

Glad to see you were able to resolve the issue by re-creating the trunk. When 3CX responds with 407 to an incoming call then it usually means that there is a problem with source identification.
That means that the PBX cannot match the inbound call to a trunk configured to your system. That could happen because the format of the numbers the provider is sending is not matching the format of the numbers in the PBX or that someone has played around with the inbound parameters of the trunk so the PBX is trying to match the wrong thing.
If the issue was solved just by recreating the trunk that indicates to me that a value in the trunk configuration of the trunk was wrong and was corrected by recreating the trunk.

 

[kelsallp]

Thanks, that's good to know.