This is a hosted IP PBX solution with a softswitch in the carrier network communicating via MGCP over the Internet with a 7960 IP phone that has the MGCP load P0M3-06-0-00. The CPE router running NAT is a 2650XM with DSL connection to the Internet. Call setup occurs properly in both directions. No ringback tone is heard when the call is initiated from the MGCP phone. Ring tone is heard when the MGCP phone is receiving a call. Once the call is connected, audio RTP stream is sent from the MGCP phone but is not received by it. I have tried enabling NAT on the MGCP phone-specific config file, but this has not helped. Any suggestions anyone? This has got to be a rather common setup for hosted IP PBX solutions from the various carriers.
