CM to PSTN - One Way Audio

Answered Question
Jan 31st, 2006
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I have a Cisco 2651 router with a NM-1V w/ a VIC-2FXO card. The router is configured and registered with the CallManager as a MGCP Gateway.


I am able to make and receive calls, but there is only one way audio. I am able to hear the party on the other end, but they can not hear me. Even if I make a call and place it on hold, the party on the other end of the line will just hear silence, and no music. I've tried calling several phones with no luck.


Here is the configuration from the router:


---------------------------------------

!

!

voice-port 1/0/0

no echo-cancel enable

timing hookflash-out 500

!

voice-port 1/0/1

no echo-cancel enable

timing hookflash-out 500

!

ccm-manager mgcp

ccm-manager music-on-hold

ccm-manager config server 10.128.0.5

ccm-manager config

!

mgcp

mgcp call-agent 10.128.0.5 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 profile default

!

!

!

dial-peer voice 999100 pots

service mgcpapp

port 1/0/0

!

dial-peer voice 999101 pots

service mgcpapp

port 1/0/1

!

---------------------------------------


I've tried everything, echo cancelation off, echo cancelation on, still the same thing, the called party can not hear me.


I also tried setting the attendant DN to the VM pilot, the system answers and then there is dead-air, so there is no audio coming through from Unity either.


Everything works great internally.

Correct Answer by agensler about 11 years 6 months ago

Can you make a test call and gather the following output from the router while the call is still connected?


show voice call sum

show call act voice brief

show voip rtp connection


Also, a show ver and the complete show run would be helpful.


Lastly, the echo canceler shouldn't cause one way audio. I would go ahead and turn that back on.

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dgahm Tue, 01/31/2006 - 17:39
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It sounds like a one way IP routing issue between the router and IP phone. The router is OK both ways to the Call Manager, but the phone is not able to send packets to the router.


If the phone is getting the incorrect default gateway it might cause this. Try pinging the phone from the router.

Kirill Klimakhin Tue, 01/31/2006 - 17:47
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That's also what I was thinking, but it's looking okay:


Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.64.6.63, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms


But it looks it's a one way issue for all the, the phone, the callmanager and the unity. Because even if I place a call on hold, the other party will not hear any hold music.

dgahm Tue, 01/31/2006 - 18:16
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Do you have any access-lists or firewalling going on?


If not, you may have a bad voice port in the router. Do you have a spare? It's also possible the line is bad, though it is pretty rare to get a one way audio issue on a POTS line. Just hang an analog phone on the line to test it.

Kirill Klimakhin Tue, 01/31/2006 - 18:21
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I have 5 different POTS lines here, all did the same one way audio issue.


No Firewall, No ACL.


Analog phone works fine.


I have tried running a CallManager Express on the same router and configured those ports for POTS, and that worked with out any kind of problems.

Correct Answer
agensler Tue, 01/31/2006 - 18:40
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  • Cisco Employee,

Can you make a test call and gather the following output from the router while the call is still connected?


show voice call sum

show call act voice brief

show voip rtp connection


Also, a show ver and the complete show run would be helpful.


Lastly, the echo canceler shouldn't cause one way audio. I would go ahead and turn that back on.

Kirill Klimakhin Tue, 01/31/2006 - 19:00
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Thanks agensler, I figured it out using the command you suggested:


ISR1.REM1.NYBKNY#show voip rtp connection

VoIP RTP active connections :

No. CallId dstCallId LocalRTP RmtRTP LocalIP RemoteIP

1 100 99 18420 20016 10.162.85.5 10.64.6.63

Found 1 active RTP connections


I recently configured a management Lo0 interface on that router, and also a management Lo0 on a MSFC on another switch. Looks like the routing was wrong on the MSFC. I took out that route, and now it's working great.


Thanks alot!

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