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New Member

voice only heard in one direction

I have a 2600 with a FXO port in it. I can dial into the port from the PSTN and get to an 7960 phone. The call gets established but the IP phone cannot hear the person calling on the FXO line, but the person on FXO line can hear the IP phone user. What's up with that? I suspect a codec issue, but I believe both the 2600 and CCM are using g711. Also the fxo line can dial extensions once voicemail picks up so some info is getting through, just not the voice.

Thanks in advance

16 REPLIES
New Member

Re: voice only heard in one direction

This may help - David Goodwin posted it to another question "voip dial peer ip address "

Mar 13, 2001, 11:21am Pacific (1.)

You are correct in your concerns. If the endpoint of the RTP stream is out a different interface on the router, than the H.323 signaling and the RTP stream can originate from different IP addresses, causing one-way audio in most cirsumstances.

The best way to solve this problem is by using a Loopback interface, and using a command introduced in 12.1(2)T that will cause all H.323 signaling and RTP streams to source from this address. Then point your CallManager H.323 gateway config to this address. Example:

interface Loopback0

ip address 10.1.1.1 255.255.255.0

h323-gateway voip bind srcaddr 10.1.1.1

New Member

Re: voice only heard in one direction

Actually, this answer doesn't seem to apply to my situation. I am controlling the gateway (2600) through mgcp using call manager. I am not using h323 in any way that I know of.

Cisco Employee

Re: voice only heard in one direction

Look at show run and make sure that you have not configured no ip routing. If you see it there, turn it back on.

New Member

Re: voice only heard in one direction

tried that, but no worky :)

New Member

Re: voice only heard in one direction

I was having the same problem with vg-200.I turned on ip routing and solves the problem.

ip routing global command.

New Member

Re: voice only heard in one direction

That doesn't seem to be my problem. Ip routing is turned on.

New Member

Re: voice only heard in one direction

I've had a few instances with one-way communication. The most common source was related to routing or addressing. I would check your addressing end-to-end. Show your IP routes and ping everything. A recent issue related to an incorrect subnet mask (typo) on an ICS 7750. I've had the mismatched codec issue be the source - just to be sure issue the codec command on the router - even if the tech docs say it's g.711 by default. Incidentally, you can tell the codec used on a call by pressing the "I"nformation button twice on the 7960.

Good luck,

Brian Carscadden

Sr. System Engineer

CCNA, CCDA, CIPT

TransNet Corporation

New Member

Re: voice only heard in one direction

I checked the phone and both the transmit & receive say g7.11u Also, everything is on the same subnet and everything is pingable from a remote subnet, so IP communication seems to be working.

Here is something weird. I changed the codec to g723ar53 and hey what do you know it works! Even though the phone says that both are using g7.11u? Go figure. I need to do more testing to see why it works when I apparently select the wrong codec, but the bottom line is that it appears to be a codec issue.

New Member

Re: voice only heard in one direction

Had a simillar issue, needed to upgrade the IOS 12.1.5T8 seems to work for us

New Member

Re: voice only heard in one direction

Well, we are already at 12.2.1 :)

New Member

Re: voice only heard in one direction

Try the global config command 'voice rtp send-recv'

New Member

Re: voice only heard in one direction

Thanks, but no luck.

Cisco Employee

Re: voice only heard in one direction

Please make sure that you have enabled the following commands in your global config:

voice rtp send-recv

ip routing

Francisco.-

New Member

Re: voice only heard in one direction

Ip routing is enabled. It doesn't seem to matter if I have the voice rtp send-recv command or not. I tried the g723ar53 codec and that seems to work for some reason. Even though the phone says that both tx & rx are g7.11u?

New Member

Re: voice only heard in one direction

It appears that I can select ANY codec on the router EXCEPT g711u or g711a and it will work with varying degrees of quality. I still don't understand why I can't select the correct codec? Regardless of the codec I select the phone still says that both tx & rx are g7.11u (I get this by pressing the "I" button twice to see the stats. Any ideas?

Thanks

New Member

Re: voice only heard in one direction

Found the problem. I was using 12.2(1) and that seemed to be the major problem. I downgraded to 12.1(5)T8 and that is what fixed the problem. I can now use g711u on the router and it works.

Thanks for all the advice.

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