Question

A network engineer is troubleshooting a persistent one-way audio problem on inbound PSTN calls that traverse a Cisco Unified Border Element (CUBE) to Cisco Unified Communications Manager. Signaling completes normally and calls connect, but the internal IP phone user can hear the PSTN caller while the PSTN caller hears nothing. Packet captures on CUBE show RTP arriving from the phone side but no RTP being forwarded toward the service provider. Which action is the most likely resolution?

Accepted Answer

Verify that IP routing and any NAT/ACL configuration on the CUBE outside interface permit the RTP media stream toward the service provider's media address range

Answer

Change the SIP transport on the CUCM trunk from TCP to UDP to allow media negotiation

Answer

Increase the maximum call duration timer in the dial-peer configuration

Answer

Regenerate the CUBE self-signed certificate and reimport it into the CUCM CallManager-trust store