QOS Issue

[ali.asghar]

What is the recommended QOS settings for Cisco IP Phones.

If all of the IP Phones belong to one VLAN then one simply enable

mls qos

mls qos trust cos on all interfaces, but what the approach should be if there is a layer III switch such as 4507 which is doing intervlan routing for multiple Voice VLANS.

I have a 4507 switch which is configured for 3 voice vlans and also doing routing for these three voice vlans. Each floor has 3750 switch uplinked to 4507 switch. I am having an issue with voice quality as well as Phone A can hear Phone B, but Phone B can't hear Phone A

On 3750, I have configured

mls qos

interface x

mls qos trust cos.

What should be on 4507 switch.

Urgent help needed.

Thanks,

[rcfoltz]

On ports where either a phone or PC/Server might be i would do mls qos trust cos and mls qos trust device ip-phone. On ports that are uplinked to other switches you should just have to do mls qos trust dscp. Also, you might want to check out the mapping table on the switches as the 3550s default mapping is not the same as qos used by callmanager. you would want to map cos value of 3 to dscp of 26 (Signaling) and cos of 5 to dscp of 46.You let the access ports determine the correct dspc value to be assigned and ust pass that value between switches.

[rbradfield]

Re the one way voice, looks like you have a routing problem. I assume the one way voice is between phones on different VLANS.

The Callmanager can communicate with the phones, because the call is setup ok. so the routing between the CCM and the phone VLANS is ok But once the rtp stream is started between the phones, only one way communication, so need to check your routing tables etc.

HTH

Richard.

[rsamtani]

As Richard pointed out that One way Voice is a routing issue. Another important thing you could check is the default gateway for the IP Phones, a wrong default gateway also causes routing issues and hence one-way Audio.