Getting Echo on outside calls??

[tcekada]

I have a Cisco 2651XM with a ISDN/PRI connection to Telco. We are getting echo on our IP phones when ever we call out to the PSTN via the PRI. No echo on IP to IP phone calls internally. I have attached a file that has a sh ver, sh run, and the output of sh call active voice commands but I just do not see anything wrong when I look at the ouput. If anyone could take a look to see if something jumps out at them that could help I would really appreciate it.

Thanks,

Tonyc

[allan.thomas]

Firstly verify the default device phone load that you have deployed across your handset. This is for the simply reason the between version 6.0.4 and 7.1.2 there are numerous updates, some of which refer to echo.

Echo is succeptible to delay, and is typically introduced through the analogue tail-end of circuit.

The perceived echo may have already existed prior to VOIP, and due to round trip delay being less than 50ms the echo could not be heard.

However due to buffering within the gateway, and packetisation, the round-trip-delay can quite easily become greater that 50ms, and hence the echo is more perceivable.

The ERL levels within the active calls are above the minimum requirement for echo cancellation to work.

For a one-way delay in the range of 25 to 150 ms, the ERL should exceed 55 dB to eliminate the perception of echo from the end-user perspective.

Verify the echo cancellation is also configured on your gateway within CallManger.

Hope this helps.

[tcekada]

Tom,

Thanks for your input. Based on that input I:

1. Updated the phones to 712, but still have echo.

2. Set the "echo cancel coverage" to 64ms in Call Manger, but still have echo.

Also, when I run the command "show call active voice" and "sh call active voice echo-canceller", the ERL value is always well below 55db as you mentioned. Any way that you know of to get the ERL values up past 55?? Also, something confusing, the Roundtrip delay is always 0 in my show call active voice commands. I attached sample in case you want to take a look.

Thanks again,

Tony

[dgahm]

You might try:

voice-port X/X:23

echo-cancel erl worst-case 3

That will allow the canceller to work with worse ERL than the default 6db. I have had good luck with this setting.