Beware - 729br8 with MGCP on 12.4(24)T, no way / one way audio

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May 14th, 2009
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Hi All,


If your gateway is MGCP and your service parameter to advertise G.729 annex-b, which is the default, you will not be able to hear audio on 12.4(24)T.


Becoming kind of a hot bug, thought I would let you know.


Details:

CSCsy10653


Symptom:

Calls on an MGCP gateway negotiating g729br8 may fail to have audio in one or both directions.


Conditions:

This occurs on MGCP gateways with the fix for CSCsu66759 when g729br8 is being negotiated.


Workaround:

Any of the following will be sufficient to get around this issue:

1. Configure the gateway for static payload type using the following commands on the gateway:


mgcp behavior g729-variants static-pt

mgcp behavior dynamically-change-codec-pt disable


2. Disable g729br8 from being negotiated for this call. If CUCM is involved, this is done with the service parameter 'Strip G.729 Annex B (Silence Suppression) from Capabilities'


3. Downgrade to IOS code on the gateway which does not contain the fix for CSCsu66759, which would be 12.4(22)T and below.






hth,

nick

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James Hawkins Thu, 05/21/2009 - 05:12
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Thanks Nick,


Saved me hours of frustration and a TAC case.

franklopez Wed, 08/19/2009 - 05:58
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FYI, Upgraded to 12.4(22)T2 per the "Fixed-In" comments and it did the exact same thing, still required the two mgcp behavior lines to have audio.


So in 12.4(22)T2 it is NOT fixed yet.


Thanks,

Frank

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