Question

A collaboration engineer is troubleshooting a one-way call setup failure between CUCM and a partner PBX over a SIP trunk. Using a SIP debug on CUBE, the engineer sees the outbound INVITE reach the partner, but the partner immediately returns a '483 Too Many Hops' response, and the call is torn down. What is the most likely cause of this behavior?

Accepted Answer

The Max-Forwards header in the INVITE reached zero before the request was fully processed, indicating a signaling loop or an excessively low starting value.

Answer

The partner PBX does not support the codec offered in the SDP body of the INVITE.

Answer

The CUBE dial-peer is missing the session protocol sipv2 command, preventing SIP negotiation.

Answer

The RTP media ports negotiated in the SDP are being blocked by a firewall in the media path.