voice rtp send-recv command

Answered Question
May 26th, 2009

Can someone elaborate on the value of the voice rtp send-recv command? According to Cisco;

To establish a two-way voice path when the Real-Time Transport Protocol (RTP) channel is opened, use the voice rtp send-recv command in global configuration mode.

Sounds like a "two-way voice path" is pretty much a given for VoIP, no?

I have this problem too.
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Correct Answer by Jaime Valencia about 6 years 4 months ago

yes, this is used in the GWs because that's where you open the channels, switches only route the RTP



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Jaime Valencia Tue, 05/26/2009 - 09:04

not really, you can have a situation where you only have a 1 way path to listen to announcements, it's usually used to fix 1-way audio issues when they're not supposed to happen intentionally

Also helps on DTMF issues

User experiences one-way audio and cannot pass DTMF digits when calling into an IVR


If you search at the TAC Case Collections for the command you'll find plenty of hits



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shikamarunara Tue, 05/26/2009 - 09:24


This is a gateway command, not usually something that's put on switches, no?

Correct Answer
Jaime Valencia Tue, 05/26/2009 - 09:36

yes, this is used in the GWs because that's where you open the channels, switches only route the RTP



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Nicholas Matthews Tue, 05/26/2009 - 16:37

This command is actually very overused. It was originally implemented as a workaround for a bug in early voice code. Since then, this command really shouldn't be doing much since the bug has been fixed since 12.2T code or so.

It made its way into some documents and now it's everywhere.

I've never solved a single problem with this command. I was able to make one thing come closer to working, but that ended up being a provider problem :)


Matt Hall Sat, 05/05/2012 - 17:50

This is an old thread, but I wanted to comment.  Although it is over used, I solved a problem just in the last 6 months with this command.  We had a situation with an h323 gateway using PRIs where all calls were completing normally accept calls to the 911 PSAP.  911 Calls where getting a one way audio situation where we could hear the PSAP but they could not hear us.  Debuggin ISDN Q931 showed that we were never receiving the "connect" message from the far end, so audio was never getting cut through.  We had to use the rtp send-recv command to cut through audio in order to get 911 calls working.

So my advice is not to use it unless you have to, but keep it in your back pocket.

wirickg Mon, 02/02/2015 - 11:12

I had to use this command on 2/2/2015 on a Cisco 2901 running IOS version 15.2(3)T2 in order to correct an issue with one-way audio on calls to 911. The gateway was configured as an H.323 gateway and was using ISDN PRI for connectivity to the PSTN. Before adding the "voice rtp send-recv" command on the gateway the site would dial 911 and could hear the 911 operator, but the 911 operator could not hear them. I added the "voice rtp send-recv" command which immediately corrected the issue, so it appears to still be relevant.


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