RE: Trust VoIP and remark Data

From: Darren Johnson (dazza_johnson@yahoo.co.uk)
Date: Thu Dec 13 2007 - 08:45:45 ART


Hey there! I believe your second option is wrong, you don't need the
override and you need to trust cos. I would do it like this....

mls qos trust device cisco-phone
mls qos trust cos
mls qos cos 1

This says trust the COS value ONLY if a Cisco phone is detected via CDP, and
any packets/frames without a COS value (such as those received from a PC on
the native vlan) use a COS value of 1. The COS override would 'override' any
COS values to 1, including COS values received from the phone!! I don't
believe you want to do this!

Dazzler

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
nhatphuc
Sent: 12 December 2007 17:55
To: Cisco certification
Subject: Trust VoIP and remark Data

Hi Group,

With question: Ensure that VoIP traffic originating from the IP phones
maintains its CoS value, while traffic originating from the PCs is
remarked with a CoS of 1

I see 2 ways to answer. The first seems to be better, but I don't see
anything wrong with the second. Which one do you choose? Please explain.

mls qos trust cos
switchport priority extend cos 1

and
mls qos trust device cisco-phone
mls qos cos 1 override

Thank you

Phuc



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