CoS rewrite between ISL and 802.1Q

[patrick.zhang]

My question is if Cisco Catalyst switch can rewrite the CoS correctly between ISL and 802.1Q encapsulated packets.

For example, packet with CoS 5 was encapsulated with 802.1Q and received by switch, if switch can write the same CoS value on the packets before sending it out on ISL link?

Apprecited for your answer!

[thisisshanky]

This should work properly. The COS received on a port should be mapped using cos-dscp map globally defined in the switch and that dscp is used to traverse through the backplane of the switch. This is an internal DSCP Only. WHen it reaches the egress port, using DSCP-Cos maps the internal dscp is converted back to COS. If these maps are set correctly, your COS value of the packet should remain same regardless of the trunking set on ingress and egress ports.

HTH

Sankar

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