From: Daniel Cisco Group Study (danielcgs@imc.net.au)
Date: Wed Apr 02 2003 - 09:11:53 GMT-3
I've researched this one heavily, but there is still something that is not clicking in my brain.....
There's lots of documentation about voice vlans, and about trusting or not trusting the COS values of packets from the PC attached to the IP Phone. All sounds very nice and useful.
However, unless a user somehow trunks to the phone, he can't set COS values anyway as these are carried in the 802.1p portion of the 802.1q header. Why are we worried about trusting or not trusting the COS values from the PC???
I'm referring to configurations like the following: (not the traditional trunking method):
mls qos
!
interface fastethernet 0/10
switchport mode access
switchport access vlan 10
switchport voice vlan 100
mls qos trust cos
In addition, what is the difference between the following:
(a) switchport voice vlan 100
(b) switchport voice vlan dot1p
Refer to doco:
http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12112cea/3550scg/swvoip.htm#51534
The Docos are very unclear..... and again, dot1p is carried within dot1q, or I've missed the boat.
Daniel
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