Unidirectionnal voice between IP phones and a BCM 400

Richard Pozywak
Richard Pozywak used Ask the Experts™
I am currently experiencing unidirectional voice traffic between our main site and remote locations.  At the main site we have a Nortel BCM400 install and at each remote site has approximately 5-12 Nortel IP-2002 & 2004 phones install.  Each remote site has a 2.4Ghz wireless link back to our main tower site and from there a 20mbs link back to the main office. Each of the sites has a Cisco 2600 router install.  At the remote sites they have a Cisco POE switch and at the main site it has a catalyst switch.   All the routers and switches have been setup with VLANs and QOS.  
The problem I am facing is that two of the sites are experiencing unidirectional voice traffic.  The users can not hear the caller, but the caller can hear them.  The configurations for all the sites are the same and the router is handing out DHCP addresses to the phones.  I have checked the phones and they are getting the correct IP address for the voice VLAN.  This problem doesnt happen all the time, it comes and goes and usually clears itself up.  If it doesnt the user just reboots the phone and it is good to go.  Any help in this matter would be appreciated.
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Les MooreSr. Systems Engineer
Top Expert 2008

Sounds like either routing or codec issue. Make sure all sites have same codecs or transcoders. Also make sure the voice vlans are properly routing between sites
Richard PozywakIT Director


I did check the codecs and they are all running the same codecs.   I have wireshark running on the network and I see no routing problems.  
Unidirectional voice often is caused by routing/firewal issues.
Have you any kind of packet filter between the sites?

Can  you look  into the voip control packets and see media address? Is it correct in the case of the call with unidirectional voice?


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