Question

A CUBE has two outbound dial peers to reach the PSTN through separate ITSPs. Dial peer 100 has 'preference 1' and points to ITSP-A; dial peer 200 has 'preference 2' and points to ITSP-B. When ITSP-A returns a SIP 503 Service Unavailable, calls fail immediately instead of rolling over to ITSP-B. The engineer confirms both dial peers match the destination pattern equally. What is the most likely cause and correct fix?

Accepted Answer

The 'huntstop' command is configured on dial peer 100, terminating the hunt after the first peer fails; remove it so the hunt continues to dial peer 200.

Answer

SIP error-code failover is not enabled by default; configure 'voice-class sip-server-group' load balancing on both peers.

Answer

The preference values are inverted; ITSP-B must have a lower preference number than ITSP-A to be tried first.

Answer

The two dial peers must use different destination patterns for the CUBE to attempt a second peer after a failure.