EXP based COS 7600 - Cisco Community

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Hi,

I have sup 720 pfc3 based 7600 with WS6XXXX Lan cards. Say we have 'mls qos' & 'mls qos trust ip prec'. The ingress & egress port are mpls enabled. There is a concept of 'internal DSCP value' in this platform. I have two questions

1. For traffic with 802.1P Ethernet frame & normal ipv4 with IP Prec , the internal DSCP mapped value is easy to understand, so on Egress side same DSCP value will be used.

2. For Labeled Ethernet frame ( without .1P ) , how the internal DSCP value is mapped, and how can this internal DSCP value rewrite EXP value on Egress.

how would exp value have an impact on QOS treatments..

Thx,

Gaurav Prakash

1 Reply 1

2. For Labeled Ethernet frame ( without .1P ) , how the internal DSCP value is mapped, and how can this internal DSCP value rewrite EXP value on Egress.

Dot1q packets will use COS (Class Of Service) marking for QoS and the 7600 has internal cos-dscp maps.

Once the dscp value is obtained, it will use another map for exp-dscp maps.

You can see your current maps with the command show mls qos maps

You may need to modify the default maps as they are incorrect, for instance COS 5 is mapped to DSCP 40 where it should be DSCP 46.

You should modified your default map with this command:

mls qos map cos-dscp 0 8 16 24 32 46 48 56
mls qos map exp-dscp 0 8 16 24 32 46 48 56
mls qos map ip-prec-dscp-dscp 0 8 16 24 32 46 48 56

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