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New Member

Echo on IP phones from PSTN

Hey all,

I’m troubleshooting an issue with echo. The problem is occurring only on PSTN calls. The issue seems to be random in that it does not happen on one particular phone all the time and it does not occur on every single call. We have CallManger 4.1(3) supporting 125’ish phones, most of which are 7941 and 7961 models. We have a single PRI in a 2811 router using MGCP. (See below config). The users complaining about this issue say they are not using the speaker phone or a headset. I also verified that the volume is not cracked to the max setting on their phones. The echo seems to crop randomly on a call and can last upwards to 30 seconds. Any hints from the group would be appreciated. The gateway load is 12.4(7).

network-clock-participate wic 0

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

!

!

isdn switch-type primary-4ess

!

voice-card 0

no dspfarm

!

!

!

!

controller T1 0/0/0

framing esf

linecode b8zs

pri-group timeslots 1-24 service mgcp

!

!

interface Serial0/0/0:23

no ip address

encapsulation hdlc

isdn switch-type primary-dms100

isdn incoming-voice voice

isdn bind-l3 ccm-manager

no cdp enable

!

!

!

voice-port 0/0/0:23

!

ccm-manager redundant-host 10.10.16.16

ccm-manager mgcp

ccm-manager music-on-hold

ccm-manager config server 10.10.16.16

!

mgcp

mgcp call-agent 10.10.16.17 2427 service-type mgcp version 0.1

mgcp dtmf-relay voip codec all mode out-of-band

mgcp rtp unreachable timeout 1000 action notify

mgcp modem passthrough voip mode nse

mgcp package-capability rtp-package

no mgcp package-capability res-package

mgcp package-capability sst-package

no mgcp package-capability fxr-package

mgcp package-capability pre-package

no mgcp timer receive-rtcp

mgcp sdp simple

mgcp fax t38 inhibit

mgcp rtp payload-type g726r16 static

mgcp bind control source-interface Loopback0

mgcp bind media source-interface Loopback0

!

mgcp profile default

5 REPLIES
Silver

Re: Echo on IP phones from PSTN

If you do a sh voice port on the T1, you will see your echo cancellation coverage - it should be at 64ms, that means you are using the newer E168 echo cancellation, which is much improved from the old stuff. If it is something else, then set it to this as a starting point, and see where you are. Then you best bet is to adjust your levels on the voice port - you want to get it so there are no volume complaints, but hopefully you crank down the signal that is being echoed back so you don't notice it. We usually start with +3 attenuation and -3 gain, and see how that goes. Here is a link to a short doc on troubleshooting echo:

http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a0080149a1f.shtml

Mary Beth

New Member

Re: Echo on IP phones from PSTN

I think I have it sorted, the issue looks like it is a bug id (CSCsd54344) related to version 12.4(7). I got a a new DSP firmware from TAC that I will try tonight

Silver

Re: Echo on IP phones from PSTN

Ah! Let us know if it clears it up, that will be one to watch for!

Mary Beth

New Member

Re: Echo on IP phones from PSTN

I was facing the same issue. I was told by TAC to try 124(5a). According to TAC in 12.4(7) and a few other loads the echo cancellers will not converge on every call. Good luck!

New Member

Re: Echo on IP phones from PSTN

I tried 12.4(2)T3 and 12.4(4)T2 and had some echo. I believe the DSPware was 6.3.4. TAC sent me the DSPware version 4.4.18 and 4.4.12, which did fix the echo issue, but it also presented a nasty issue of voice cutout on the IP phone side during the first 10 seconds of about 95% of the calls. I upgraded to 12.4(6)T2, removed the DSPware file they sent me from flash, so it used the built-in DSPware in 12.4(6)T2 which is 7.4.1. I made about 30 calls and didn't have any echo or voice cutout.

Hope this helps! If so, please rate.

Thanks,

Kevin

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