Remote Call Drops

[khanfawaz]

Hi

There are two cucm clusters. One is cucm 5.x and the other one is unknown because its taken care by some other. When a call is made from CUCM 5.x cluster to the second cluster, the phone registered to the second cluster rings but if someone answers the call, the call drops. But vice versa its working fine. ie The calls from the second cucm cluster to the CUCM 5.x is working fine. All other calls are working fine. Is there any other possible causes other than codec mismatch and firewall blocking the rtp stream? What else I need to check? Thanks in advance. Please help..

[phooghen]

Did you try to enable Media termination Point on the ICT (Inter Cluster trunk) on the CUCM  5.x ?

Did you check the codec used, don't you need transcoding resources ?

Pierre.

[khanfawaz]

I did not try to enable MTP. I do not think transcoding resource is required as it was working fine all these years. And I beleive that even if any transcoding resource is required, it should be on the second network's end because the codec transcoding should be happening on their end and not our end.

[elaverriere]

I had a very similar issue not too long ago, which was caused by a firewall change. My FW team inadvertantly blocked the traffic for the audio stream (UDP 16394 - 32767) but not the traffic for the voice control packets.

Along those same lines, you must have routing in place for phone subnets between both sites as after the call is setup by your CUCM server, it hands the call off to the endpoint on each end and if your network doesn't know how to get back to their endpoint network the call will drop.

[khanfawaz]

Hi elaverriere,

Thanks for the reply. The issue is resolved now