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

[Nicholas Matthews]

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

[James Hawkins]

Thanks Nick,

Saved me hours of frustration and a TAC case.

[nds-frank]

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