From: Dennis J. Hartmann (dennisjhartmann@hotmail.com)
Date: Mon Apr 25 2005 - 18:57:56 GMT-3
On ingress to the switch, the CoS value will ALWAYS be mapped to the
DSCP value if it's a .1Q trunk. If the COS is 0, the DSCP will also be
ZERO. You must configure DSCP-Pass Thru on the switch to override the
COS-DSCP mapping and then use the MQC to classify upon DSCP 25 and mark DSCP
20 on SW1. You must also configure the trust boundary for DSCP on SW1 and
SW2 to trust the markings coming from the other switch.
To test this, do an extended ping from R6 with the ToS byte set to
100 (you have to know how to map the DSCP back to the ToS value) and make
sure that this value is being received correctly at R3 (SW1 and SW2 is the
tricky part).
Here's the issue for verification. I don't believe a debug ip
detail is going to show you the DSCP values received. To see this, I think
you're going to have to turn on IP Accounting and/or NetFLOW and use the
necessary show commands to see your ToS value (in hexadecimal).
Have fun with that. Let me know how you make out. I'm curious
myself. The CoS-DSCP and IPPrec-to-DSCP and DSCP-CoS mapping tables are
critical. The easiest way of bypassing them is to configure
dscp-pass-through.
Sincerely,
Dennis Hartmann
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of aji
nc
Sent: Monday, April 18, 2005 9:20 AM
To: ccielab@groupstudy.com
Subject: Switch Qos policy-map or prec-to-dscp map
Hi, All
Diagram
=======
r6----sw1----sw2----r3
traffic is coming from r6 with ip precedence 7 set it should be marked with
dscp value of 25 in sw1 and traffic from sw1 to sw2 should be marked with
dscp 20 traffic marked with dscp 20 should be marked with ip precedence
critical, Question from NMC labs
I thought i can use a prec-to-dscp map on cat1 and a dscp-to-dscp
mutaion map in cat2 because there is a trunk between cat1 and cat2, At r3 i
can use a policy map to match dscp and set ip precedence,
My doubt is whether i can use policy map at sw1 for setting the dscp
based on ip precedence?
how do I differentiate what to use in the real lab ?
Thanks
Aji.N.C
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