7921 no outbound audio (pots calls only)

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Nov 5th, 2014
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I have an odd problem.

I have a 7921, which registers as it should in an CUCME 8.6 environment.

4 ephones, (3) 7975G and (1) 7921. One incoming / outgoing pots line. No voip.


My problem:

calls made from the 7921 to internal extensions work perfectly. Audio in both directions.

Calls made from the 7975's to internal extensions and external numbers work perfectly - audio in both directions.

Calls made from the 7921 to external numbers, however, have no outgoing audio. Inbound audio works fine.


Any ideas? Config is attached

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Tagir Temirgaliyev Wed, 11/05/2014 - 22:15
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probably 7921 have another default codec than 7975 and you do not have transcoding

please provide

sh ver

sh inv

sh runn all


sh call voice med com

when you doing all 3 types phone call

Darren Watts Thu, 11/06/2014 - 08:57
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sh call voice med com doesn't work for me, on any of my routers.

I have attached logs for both sh voice call sum and sh voice dsp. The calls are being handled in g711ulaw exclusively regardless of which phone is calling where.


I did note that both internal and external calls to and from the 7975s persistently use one dsp port (50/0/1.1), while both internal and external calls to and from the 7921 persistently use a different dsp port (50/0/10.1)

Not sure if that has any significance, or why different phone types seem to be locked to a particular dsp port.

Darren Watts Thu, 11/06/2014 - 18:01
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This turned out to be a NAT issue. Relocating the 3rd party WAP to the voice switch, where it can participate directly in the VLAN structure there, resolved the issue.

I currently have an ISA550 bridging two routers and acting as the gateway to the internet. I believe the problem lies in that box. I'll be replacing it shortly and using my 2901 as my internet gateway.


Thanks for all help


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