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"Sudden" one-way audio with 2821 - CCM w/ MGCP

I have 3 2821 voice GWs configured as MGCP for 3 PRIs. (NO MultiLink bundle, just round-robin hunt for the DIDs) I have had several incidents of one-way audio on IP Phone -to -PSTN calls, where the external caller ( on the PSTN side) will be able to talk and hear fine, then, randomly, will not hear anything at ALL! The IP phone user hears the outside caller speak, but the PSTN caller can't hear the IP phone user. It's just like in the middle of the conversation, the call drops, but it is actually a "one-way audio" issue. THIS IS NOT A ROUTING ISSUE, as I have tested the bloody thing seven ways to Sunday all day today!! The CallManager's are all 4.1(3), IP phone loads are 7.2(4), and the 2821 IOS is 12.3(11)T7. The IP phone / Voice GW / CallManagers are connected as diagrammed below, with DHCP being done on the 2821s for VOIP ONLY, and the 6500 doing ALL the routing, running CAT OS 7.3:

3550----------6500-------------3550--------IP Phone

| |

| |

| 2821 Voice GWs

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|

|

CallManager

This is a VERY "hot-button" issue with this customer...

PLEASE HELP!!!

3 REPLIES

Re: "Sudden" one-way audio with 2821 - CCM w/ MGCP

Does the audio come back at all , or do they just hang up when it happens?

When it happens, if you can keep a call up... can you look at the receive/transmit packets on the phones web page for the stream to see if packets are incrementing in both directions or one direction?

Not to beat on the network or routing anymore then you have, but are there any IP phones in same subnet as gateways that the issue happens on?

How often does it happen? Do the gateways have the mgcp bind command, etc or just using LAN interface for same subnet?

Silver

Re: "Sudden" one-way audio with 2821 - CCM w/ MGCP

We have been noticing a lot of one-way audio issues lately, that frequently won't clear without a router reload. This has been mostly on 1760s, but I wonder if it could be related? We will see the following error in the log:

%IPM_C54X-3-HOST_XMIT_BLOCKED: Host is unable to transmit packets to DSP 0

Mary Beth

Silver

Re: "Sudden" one-way audio with 2821 - CCM w/ MGCP

Oh, and ours are not doing MGCP in these cases. Again, maybe not related, but do you have to reload to clear your condition?

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