We have the cisco 2951 setup and running, however, if someone externally calls us and tries to leave a voicemail it disconnects after 14 seconds. Not sure what the problem is and no one else seems to know either. When we get the voicemail in the inbox it says Disconnected [No RTP Detected]. Any help would be greatly appreciated!

It sounds like maybe the gateway is not sending the RTP to the CIC server and this is why the call disconnects with no rtp detected. Can you provide the Cisco IOS you are running on the gateway as well as if you have any media servers? As a quick test you can try unchecking "disconnect on broken RTP" on the SIP line > configuration > Session. Unchecking this will allow the call to stay connected even if there is no RTP, however since RTP carries the audio it is possible that there will just be silence in the voicemail.

IOS version is 15.0(1r)M6. So what I did was put the gateway back in our dev environment and put the old gateway in production and tried to leave a voicemail. It worked in dev, I left a message for over a minute. So that pretty much rules out the gateway. Well sort of, some configuration in production for CIC is different than in Dev. I can try that disconnect and see.

What are the configuration differences between dev and prod?

The only difference I can see is in the lines. The transport protocol is different. In Dev it is TCP and Production it is UDP. I am going to try to change this and see how it goes.

I tried changing the protocol and that didn't affect it either. Kinda stumped.

Have you tried turning up TSserver and SIP engine logging to see what the system is doing when you having the issue? I can tell you that line protocol changes from UDP to TCP are actually a rather big deal since that changes how the SIP messaging and RTP gets to you.

I finally got it working this morning. I changed the sip config on the gateway to udp and put it back into production since that is how our external lines configuration is configured in IA, the phones were using TCP which enabled it to make calls in but the voicemail was getting cut off. Once I put everything back into place it is now working. Thanks so much for your help!!