From: Antonio Soares (amsoares@netcabo.pt)
Date: Wed Jul 11 2007 - 20:40:25 ART
The switch forwards the frame over the trunk with cos=5 AND dscp=40 (default
cos-dscp table).
You can test this easily issuing the commands "show mls qos int INCOMING-INT
statistics" and "show mls qos int OUTGOING-INT statistics" on your switch1.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Frank
Sent: quarta-feira, 11 de Julho de 2007 22:24
To: Cisco certification
Subject: cos/dscp
Hi,
i have a question regarding the cos/dscp mapping between switches that are
connected by trunks.
If i have the following setup
phone -trunk- switch1 -trunk- switch2 -
And the phone marke with cos5 for the voice traffic. I know the switch needs
an internal DSCP value for mapping to queues.
So the cos-to-dscp mapping maps cos5 to DSCP 46 for example. Then the switch
need to forware the frame over a trunk.
Does he need to convert the frame to a cos value again? Or is the frame
encapsulated with the new DSCP marking into an 802.1q trunk frame and on the
other side the switch can handle the frame with trust dscp on the trunk?
Or does the switch had to convert the frame from internal dscp to cos again
and then queue it regarding the cos value and then the other switch receives
it depending upon the cos to dscp mapping.
So are dscp to cos mappings also needed on the first switch?
I hope i made my question clear enough.
Frank
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