one-way audio issue only between two ip phones

Unanswered Question

I have two 7941G's operating on the same subnet and registered to the same call manager only experiencing one way audio when sending or receiving a call to each other. Each affected phone IS able to call any other IP phone both on the same subnet or any other throughout the wan. I've verified RTP packets are being sent and received through the default-gateway and no voice gateway is involved. Thoughts?

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sadbulali Mon, 08/13/2007 - 12:59
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The PSTN calling party is not able to hear the greetings configured on Cisco Unity. The Cisco Unity Port Status monitor shows that Unity answers the call. Cisco Unity sends the greeting audio stream to the caller, but the calling party is not able to hear the greeting. Internal calls to Cisco Unity function properly, and callers are able to hear the greetings.

This is a one-way audio issue that affects calls through the PSTN [gateway] into Cisco Unity. This problem results when Cisco Unity sends the Real-Time Protocol (RTP) packets to the wrong interface on the gateway. For example, Cisco Unity sends packets to the loopback interface instead of the FastEthernet interface, which is the "bound" interface for the Media Gateway Control Protocol (MGCP) process.

mwadam Mon, 09/24/2007 - 14:45
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I am having the same problem. Mine started when we configured the gateway to source MOH from flash. I added a loopback interface with This address is not routeable anywhere in the network. It is only used for MOH from flash. The odd thing is when PSTN callers do not here audio from Unity, if you issue a route print on the Unity server, the address shows up automatically in the route table. I can delete it but it always reappears. I have three other gateways in this network all with the same config but they do not have this problem.

Were you able to solve your issue?



mwadam Mon, 09/24/2007 - 15:22
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Fixed it. A bug in MGCP is causing the loopback interface to be the source for RTP packets from Unity. Upgraded to 12.4.15T1 and solved the issue.

AJAZ NAWAZ Mon, 08/13/2007 - 13:40
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hmm.. that's strange. if both phones are on the same subnet, both phones should be sending RTP Voice to each other directly?

why are they forwarding to a default-gateway?

are we missing something here..

does the subnet span across disparate locations?

Come back to us so we can try to make sense of this with a view of course to resolving this oddity.



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