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Callers cannot hear each other on a CP-7937G

j-leverett
Level 1
Level 1

Callers cannot hear each other on a CP-7937G. The phone registers with the Call Manager. Calls connect but the calling parties cannot hear each other. Has anyone seen this as a quick got ya / symptomatic of a known issue or common scenario? The phones are separated from the Call Manager by office geography, but other desk phones (6941) are working correctly from this site and we have compared configs in a general sence.

Thanks,

Jason

3 Replies 3

Jaime Valencia
Cisco Employee
Cisco Employee

That's usually routing issues, not config issues in CUCM.

You can also try upgrading to the latest FW and see if that helps.

HTH

java

if this helps, please rate

www.cisco.com/go/pdihelpdesk

HTH

java

if this helps, please rate

Thanks for the response. We kinda came to a similar conclusion while looking into this further. A colleague suspected that it might have something to do with the codec the phone was using. Other 3937 phones are using G.722 whereas this one is using G711Mu. We read somewhere that you could override this within the phone config in CUCM, but the version we have (7.1.5.31900) does not seem to support that.

If you really want to get to the buttom of this, you need to do a wireshark capture and look at the start transmition SCCP signal that  the phone recieved from the call-manager. In there, you will see the codec, port number and ip address that call manager gave each phone to use to speak to each other. If you look further, you will also see if the phones are actually trying to speak to each other because you will see the RTP streams leving the phones. If the phones  are actually trying to speak to each other but the RTP packets are not getting to the other phone, then you can safely say that the networking is either not delivering the audio packets or it is blocking it from ariving. Here is a video guide on how to do this, its really easy:

http://voiceinitiate.com/2013/04/15/investigating-one-way-or-no-way-audio-part-1/

Since these are not soft phone, you will need to configure span so that you can capture the packets at switch level and push it to another swithport where the PC running whireshark will be on. Here are links on how to configure SPAN port:

http://ipexptobe.blogspot.co.uk/2011/09/span-how-to-easy-configure-port-monitor.html

http://www.cisco.com/en/US/docs/switches/lan/catalyst2940/software/release/12.1_19_ea1/configuration/guide/swspan.html