One way audio between 2 phones on same subnet

[Maxim Denisov]

Hello,

I faced a problem with 7911 phone. When subscriber initiate a call sometimes remote subscriber can't hear him. I caught this call between him and 7961 phone on the same subnet. During this call I opened stream statistics on both phones and saw that RTP addresses and ports are correct and sender/receiver octets are increasing, the codec was G.722. I have replaced 7911 phone with another one, deleted and added the phone in UCM without success. Phone firmware is SCCP11.9-2-1S, UCM version 8.6.2.20000-2.

Is this a firmware bug? How can I solve this problem?

Regards,

Maxim

[Carlo Poggiarelli]

Hi Maxim

Please disable G722 codec advertisment under "Enterprise Parameter" and try again.

IP Phones 7911 support wideband codec with an optional wideband Handset or Headset.

http://www.cisco.com/en/US/prod/collateral/voicesw/ps6788/phones/ps379/ps8537/prod_white_paper0900aecd806fa57a.html

http://www.cisco.com/en/US/prod/collateral/voicesw/ps6788/phones/ps379/ps8737/product_data_sheet0900aecd806aab2b.html

HTH

Regards

Carlo

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[Maxim Denisov]

Hi Carlo,

Thank you for quick answer.

I don't want to disable G.722 clusterwide, I disabled it on the problem phone instead. Since the problem not repeated constantly I need a time to collect statistics. I don't think that the problem is in the codec because everything works perfectly on many other 7911 phones.

Regards,

Maxim

[Carlo Poggiarelli]

Hi Maxim

To verify if the issue is codec related, you can also see call statistics on the phone during an active call and see if nagotiaded codec is g722. Working call may have G711 as negotiaded codec.

HTH

Regards

Carlo

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[Maxim Denisov]

Hi Carlo

The problem is not reproduced on every call, most of the calls works as intended. 10 times the call to the same phone goes right and on the eleventh the problem may occur. I have no ideas how to debug this.

Regards,

Maxim

[Dennis Mink]

Debug you can use RTMT and collect call manager trace files.  You will need to inform your users that in the case where they come across one way audio, they document the called or calling number and timestamp. Use this info to do trace file collection.   You will have to bear in mind that interpreting tracefiles, is a black art becuase Cisco has no documentation on how to interpret them (unfortunately).  make sure you set the tracefile level to detailed

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[Maxim Denisov]

I have some experience using RTMT and don't think it will show something usefull because endpoints getting correct RTP parameters with signalling point of view but I will try. What should I look at in these traces?

[Adam]

Maxim,  did you ever find a solution to your one way audio issue?

Thanks,
Adam

[Maxim Denisov]

Hi Adam,

I found that my problem is a network problem. There were problem with third party wifi access points. There were 2 APs with different SSID and they somehow relayed MACs from LAN ports to each other by air. I found this on Catalyst ports.

Regards,
Maxim

[Christian Semmler]

I had once a similar problem: At the end it was an old switchport configuration which create a static entry in the switch mac table. So the media was send to the wrong switch port.