Wednesday, December 10, 2008

IP Telephony

In this post an ip phone is attached to fa0/5 on a switch. The requirement is for the switch to mark the voice vlan as 10 and data as 100. The COS value from the phone should be trusted and the switch needs to instruct the phone to assign cos value of 1 to data.

mls qos
vlan 10

int fa0/5
switchport voice vlan 10
switchport access vlan 100
mls qos trust cos
switchport priority extend cos 1
N.B. unlike data, when a voice vlan is assigned on an interface the vlan is NOT automatically created on the switch.
N.B.B without any instruction, the cisco phone will mark all data packets with a COS value of 0.

The necessary config for voice on a 3560 can be cribbed from the 'VOICE Vlan' section under the 3560 configuration guide.

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