Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.


Voice Activity Detection

Hi all,

I have a CallManager that is Connected on the ISDN via Cisco 2620 Gateway.

VAD is disabled on the dial-peer and SilenceSuppressionSystemWide is off (set to "F") on the CallManager.

If I look in the "Call History" on the Gateway VAD is enabled for outgoing calls from IP Phones.

Is there a failure in the Call History or is VAD really enabled ?



New Member

Re: Voice Activity Detection

If your Cisco 2620 is operating as an H323 gateway, it could be the pid used for the outbound leg of the outbound call.

Make an call to the outside through the gateway. If you then issue a "Show call active voice brief"

This will display several lines corresponding to the call legs of the h323 call. You should notice the listed pid number for each call leg. If you notice any of the pids showing pid(0) then it is using the default pid. The default pid has VAD enabled. The default cannot be modified, so you have to tell your h323 gateway which dial-peer configuration you want to use for the outgoing leg of your h323 calls.

This can be done by adding an incoming called-number statement to one of your dial-peers

For example if you the following dial-peer configured:

dial-peer voice 10 voip

preference 1

destination pattern 2000

session target ipv4:

no vad



You could add the following line to that dial-peer

incoming called-number .

and any outbound call would then have a match and would use the no vad statement from this dial-peer.

If you again place a call and show the active call you should see the outbound call leg on pid(10) instead of pid(0).

Hope this helps...


Re: Voice Activity Detection

Hi James,

Thanks for your Help.

The Outgoing Calls from Ip Phones have all the PID (0).

I will attempt to realise your suggestion.

thanks again



Re: Voice Activity Detection


I have configured " incoming called-number .. "on the Voip dial-peer it works fine regarding VAD. But the problem is i have still 2 other dial-peers for fax transmission. The command "incoming called-number.. " on the voip dial-peer in direction call-manager effectuar that all calls take this dial-peer in the backward direction. The consequence of that is that i can receive fax but not send any fax.

Can I disable VAD when i set the command "voice vad-time " to 65536 ?