Echo to PSTN through PRI

Unanswered Question


I recently changed from a 3725 w/nm-hdv/wic-1mft-t1 to a 2821 w/vwic2-2mft-t1e1. I had default voice-port settings no the 3725 with no report of echo for 2-years. After moving to the 2821, I am getting numerous reports of echo to/from the PSTN on the side of the IP phone user.

I have a TAC case, and have verified no slips on the controller, and have played with the input gain and output attenuation. For now, those are at -4,4, and I'm still getting echo.

My TAC engineer has now asked that I capture calls on the gateway, which I am working on doing.

The question is, should I try anything else, or is there anything else that I can do to troubleshoot other than playing with the in/out gain?

I have attached a show tech.

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Overall Rating: 5 (2 ratings)
mmorris11 Fri, 04/13/2007 - 13:18
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what version ios you running?

I'm on 12.4(3g).

I had been through that link already, and had specifically asked the TAC engineer if this could be a dspware issue, and he said that it was resolved for 12.4(3g). The dspware version is 4.4.20.

I have not personally been able to hear echo on a call yet, but the users that have complained are saying that it makes the call almost inaudible.

johnnylingo Mon, 04/16/2007 - 08:24
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If it helps, I have hardware nearly identical to yours and haven't encountered any echo problems with IOS 12.3(11)T11 or 12.4(7e). 12.3(11)T11 has DSPware 4.4.709 and 12.4(7e) has 4.4.24

I *did* however have a fair amount of echo problems with IOS 12.3(11)T10, although unfortunately I can't recall what DSPware version it came with.

TAC asked me to get a packet capture of a call with echo. I was able to get one, and the IP phone user even complained to the person she was talking with that she could barely understand what the pstn user was saying due to hearing herself echoing back.

I listened to the call, and there was zero echo based on the capture. What's next?

johnnylingo Fri, 04/20/2007 - 14:20
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I'd try a different IOS version. Would suggest 12.3(14)T7 or 12.4(7e) based on the feedback I've received here.

paolo bevilacqua Fri, 04/20/2007 - 15:13
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Hmm.. if the recording has no echo then the next source can be the phone only... Which FW are you running on the phone ?

Also what mean "could not understand the other person"? When you suffer of echo you have trouble when talking, not when listening to the other person. Unless both persons where trying to talk at the same time, as sometime happens.

lwai Fri, 04/20/2007 - 19:47
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Hi All,

I suggest upgrade to Version 12.3(14)T7, my client also use Cisco2821 voice gateway and

do not encounter any echo issue.

The site have around 600 phone sets.

When I listened to both streams at the same time, I heard no echo, but when I listened to just the reverse stream, I heard the IP phone users voice echoing back through.

Some of the users that have complained have said that they are hearing themselves come back through at the same time the other person begins talking.

TAC found a bug CSCei36520 - ccCaps not initialized properly in DSMP. The engineer was not certain that this echo was a cause of this problem, but in any case 12.4(7e) was recommended by TAC. I'm glad to see others here recommend it.

I upgraded last night, and am keeping the capture going, and will hope not to hear any reports of echo.


MARK HOLLOWAY Sun, 04/22/2007 - 09:37
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I use several AS5400's as SIP to PRI gateways to Nortel DMS switches. When I first turned up service I had to work with the voice-port settings to get rid of echo. See if my settings help your configuration (assuming the commmands carry over to your IOS on the 2800)



voice-port 1/0:1:D

input gain -3

output attenuation 3

echo-cancel coverage 64

no vad

I'll bet you it's a DSPWare issue. Check out Cisco bug CSCSD54344.

give the bug a look, try an IOS upgrade, and see if it doesn't make your life a lot easier.

Upgrading to IOS 12.4(11)T or later has saved my bacon at numerous customer installs that were all having echo trouble with anything that had a 5510 DSP chip in it.


thanks for the post. This has been suggested in previous posts in this thread. I had asked my TAC engineer this same question even though 12.4(3g) was not listed as being affected. The dspware in that release was 4.4.20.

After my upgrade this weekend to 12.4(7e), the dspware went to 4.4.24. I hope that TAC is wrong and the dspware issue was my only problem, but I guess we'll see. I've gone almost 7 business hours without a complaint, but another day or two and I'll be more confident.



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