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Echo Problems on 7750 - MRP

Unanswered Question
Dec 4th, 2002
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we have 2 MRP300's used for PRI's

IOS is 12.2(8)

echo cancellation was 8 then changed to 32ms

we are still having echo problems (echo on th IP phone side) to

the PSTN - local or LD

PRI's are in route list using - PRI2 first then PRI1

also having problems with certain faxes only tranmitting about 50%,

we turned off ECC (seemed to help a little) but problem persists

appears to be related to noise -

echo and fax issue related ????

please help - urgent

thanks in advance

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dave.easton Fri, 12/06/2002 - 14:06
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I was experiencing same problems with similar equipment. I was unable to totally eliminate the echo in calls to the PSTN. If you read cisco's echo troubleshooting docs, most echo is created in the network in equipment you have no control over. If your users are hearing their own voices coming back to them in a delay, odds are that echo cancellation out in the public network is not working properly. There can also be echo created when voice signals traverse 4-wire facilities, are converted to 2 wire, and back again to 4 wire. Again, other than not calling those destinations or possibly pick-coding, you cannot control that.

I got the most success from a low-tech approach. I was able to eliminate many echo problems by getting users to turn the volume down on their phones when they were on the speaker or headset. I also pumped up the echo cancellation on the gateway. If you make any discoveries, post it for us....

I know this wasn't much help Darren, but maybe some echo experts will crawl out of the woodwork and enlighten us.

darren.staples@... Tue, 12/10/2002 - 08:28
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Actually there is a Callmanager bug with MGCP gateway - that is callmanager overwrites defaults back to MRP when it registers with the call manager.

therefore: echo-cancellation, gain & attenuation changes on the MRP, do absolutely no good - should be rectified in CCM 3.3 ???

darren.staples@... Mon, 12/16/2002 - 18:12
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Cisco found a new IOS release 12.2(13)T, which has echo suppression - only problem is that it's for a MRP 200 (not 300) - nor did any of the documentation state that. We tested it anyway - works fine except if the router reboots - will not load the config as is looking for a TFTP server (MRP 200 has no flash)

anyway we are installing 12.2(yn) tonight - this version changed type of echo-cancellor (from previous version - the existing version installed with some echo problems is 12.2(8)YM - the echo is at the beginning of the call for about 5 seconds and then drops (80% of calls))

aungureanu Sun, 12/22/2002 - 19:29
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I started to have echo issues only after I got my 3725 to use the CM as the config server. (your information that there is a bug in the MGCP makes sense and I will verify it by not allowing my CM to configure my 3725)

I have loaded the 12.2.13T and using the echo canceler and it works great. I do recomand it.



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