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New Member

VoIP Side echo... I'm stumped

      We've been having an issue lately where one of our sites is reporting echo that is heard only by the person talking on our end. They report hearing their own voice repeated back to them. Being 90% sure that it was only on external calls, we had our PRI tested by TELUS, the provider, who found errors at first (the site is remote and connected to the PSTN over many repeaters), but then did stress testing and said it was fine... He's suggested that it must be on our end, though the fact that he calls it the "analog side" gives me doubts that he knows what he's talking about.

We're running a few different models of phones, though mainly 7941s, 7942s, and 7961s.

CUCM Version

For switches we have a few 3560 8 ports, and mostly 3560 24 ports. The voice gateway is a 3825.

Is there anything that could be causing echo on our end? Nowhere else on this large cluster are we hearing this type of echo.



Re: VoIP Side echo... I'm stumped

Are the users on speakerphone? If so, if the volume is cranked up to full it can cause issues with echo cancellers. Also ive seen this with certain headsets.



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New Member

Re: VoIP Side echo... I'm stumped

Right, I forgot to mention, that's the thing: they're mainly using only the receiver (handset). Lowering the volume helps, but doesn't eliminate it completely.


Re: VoIP Side echo... I'm stumped


Here is a link to troubleshooting echo.

Can you also check that you are clocking the ISDN properly

Something like this depending on the slot etc of the T1/E1 controler



network-clock-participate wic 0

network-clock-select 1 T1 0/0/0



Regards, Alex. Please rate useful posts.
Hall of Fame Super Red

VoIP Side echo... I'm stumped

Hi Tyson,

Just to add a note to the good tips from Chris and Alex (+5 guys!)

One common spot for echo to be generated in an IP network is with

the voice DSP's within your gateway (3825) one general quick fix is

to try and reboot the router/gateway. Then look into what IOS you are running

as when you upgrade the IOS you also upgrade the DSP version within the

PVDM's on the gateway. There were some well known echo/DSP related issues in

the earlier 12.4.x code.



New Member

Re: VoIP Side echo... I'm stumped

Thanks guys. The thing is that we're running DSPWare version 9.4.5 and IOS 12.4(13r) and I don't think they're included in the problems. One thing I got, though, is an output from "show controllers t1" (this is after resetting the counters yesterday)

  Applique type is Channelized T1

  Cablelength is long gain36 0db

  No alarms detected.

  alarm-trigger is not set

  Soaking time: 3, Clearance time: 10

  AIS State:Clear  LOS State:Clear  LOF State:Clear

  Version info Firmware: 20071011, FPGA: 13, spm_count = 0

  Framing is ESF, Line Code is B8ZS, Clock Source is Line.

  CRC Threshold is 320. Reported from firmware  is 320.

  Data in current interval (30 seconds elapsed):

     0 Line Code Violations, 0 Path Code Violations

     4 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins

     4 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

  Total Data (last 24 hours)

     5549 Line Code Violations, 39 Path Code Violations,

     9758 Slip Secs, 0 Fr Loss Secs, 26 Line Err Secs, 22 Degraded Mins,

     9779 Errored Secs, 5 Bursty Err Secs, 1 Severely Err Secs, 0 Unavail Secs


Re: VoIP Side echo... I'm stumped


Can you check that you are using the correct clocking as you are suffreing clock slips

look at

show network

What is the router using as its clock for the TDM

If you post the results and show run we may be able to help you.



Regards, Alex. Please rate useful posts.
Hall of Fame Super Red

VoIP Side echo... I'm stumped

Hi Tyson,

Even though 12.4(13) is not shown in many of the bugs related to echo and

DSP's we were still having echo problems with later version like 12.4(15).

It's probably more related to clocking/slips as nicely suggested by Alex but I

thought I should just add this for your reference



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