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Monday, September 19, 2011

DSCP to COS map (table-map) on Nexus 7000

We have an application that is marking using DSCP values. All of the switchports are configured for Layer 2 and we would like to leverage queuing.
As we understand it, DSCP is useless for queuing as it only cares about COS. So we started to create a table-map.

However when we try this on the actual Nexus (running 5.1.4) and this is what we get:

test1(config)# policy-map qos_apps
test1(config-pmap-qos)# class
class-default qos_apps type
test1(config-pmap-qos)# class qos_apps
test(config-pmap-c-qos)# est ?
% Invalid command at '^' marker.
test1(config-pmap-c-qos)# set ?
cos IEEE 802.1Q class of service
discard-class Discard class
dscp DSCP in IP(v4) and IPv6 packets
load-sharing Load sharing across ECMP by set out-of-order bit
precedence Precedence in IP(v4) and IPv6 packets
qos-group Qos-group

It looks like we cannot map Cos to DSCP because if I try it, it rejects:

test# set cos dscp
% Invalid number at '^' marker.

With nexus there are default classes for ingress can not be removed but you can change it and also they differ depending on the I/O model used like the 10G M1 has 8q4t queuing classes

Please click here to find the best practice recommendations from cisco when you implement your N7K qos

Also for your above question please click here to see the guide for older version. It describes it clearer as you might need to use class and policy type of qos

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