one way audio issues

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Aug 31st, 2009
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Hello All,

I had a 3-PRI trunk terminated into two seperate Cisco 2851VGs working fine - in an effort to consolidate gateways we added an additional VWIC to GW#1 and terminated the 3rd PRI into it - circuits looked clean, no errors but we began having one way audio issues as well as hearing other employees conversations from their desk phones, hearing faxes coming through the IP phones - real strange stuff, only on PSTN calls. After trying to troubleshoot for a while we resorted to moving the circuit back into the GW#2 and the problems ceased. The LEC says there is no need to change anything if we are moving he physical PRI to another box. I've got 2 PVDM2-64s in GW#1 and just 1 PVDM2-64 in GW#2 so don't think I have a DSP issue - Has anybody come across a similar situation?

Thanks in advance!

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Nicholas Matthews Tue, 09/01/2009 - 14:29
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There is a bug on the gateways that will do this: CSCsg47594

Check your flash for any .rbf, guido, or hdv2 files, as those are manual DSP firmware upgrades that can also cause this problem.

I have only seen 2 causes of crosstalk - this bug, and when the provider is mixing the channels on their side. If simply switching gateways resolves the issue, I would hope it would be this bug.

There are also some odd occurrences of this with IPCC I believe, but I'm not intimately aware of any of the details.

Hope this helps.


pcaltagirone22 Tue, 09/01/2009 - 15:43
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Well, we thought the issue ceased when we moved back to the original config setup but the problems resurfaced full force today - still cannot get to the bottom of it. It is hit or miss - doesn't happen all the time to all calls. I do not see any files in flash like you referred to so don't think it is related to that bug. Real strange hearing crosstalk from another IP Phone though - instead of hearing the other party on the line we get the voice stream from another internal phone. We do have a VG224 at the site but no FXO/FXS ports on the gateway either. Will keep working on it. Thanks for your reply!!

Nicholas Matthews Tue, 09/01/2009 - 15:55
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This bug is not restricted to FXO/FXS. It will happen on any router that has an analog port (PSTN) connected, and if you're using conferencing or transcoding on the listed IOS versions.

I would check the IOS versions of your gateways. Otherwise, it could very well be a provider problem. I would open a case with them to see what they say. You may want to get more details - like record the time and which channel of the PRI you're on while it happens.


pcaltagirone22 Tue, 09/01/2009 - 16:03
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I was having trouble logging into CCO so I didn't read through the complete bug info and assumed it was just FXO/FXS port related - I will take a deeper look and see if my IOS version is affected. As for the provider, i contacted them and they tested and said all was good from their end. The PRI channel was unfortunately very arbitrary when it happened. I really couldn't pin it down to one particular PRI or specific channel on a PRI. It is probably one of the weirdest issues I have come across in a while - Thanks again for you reply!!

I'll post back when I get resolution.


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