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Table 15. Example CoS Mutation Mapping

Original CoS Value Mutated CoS Value for Threshold Management

0 3

1 0

2 2

3 4

4 1

5 5

6 7

7 6

In the example map above, an ingress frame with a CoS value of 4 will take on the mutated value of 1 when placed

in the queue. Should the threshold where CoS value of 1 is mapped to be exceeded, then that frame (with the

original CoS value of 4) will be dropped.

This feature can only be applied to an 802.1Q trunk port whose trust setting is set to trust-cos. This feature is also

only applicable to select linecards including the following: WS-X6724-SFP, WS-X6748-GE-TXm WS-X6748-SFP and

WS-X6704-10GE. When CoS mutation is applied to a port on these modules, all ports in that ASIC port grouping

also take on this feature. Port groupings are defined as follows:

Table 16. CoS Mutation Port Groupings on WS-X67XX linecards

Module Number of Ports Number of Port Groups Port Grouping

WS-X6724-SFP 24 2 1-12, 13-24

WS-X6748-SFP 48 4 1-12, 13-24, 25-26, 37-48

WS-X6748-GE-TX 48 4 1-12, 13-24, 25-26, 37-48

WS-X6704-10GE 4 4 1, 2, 3, 4

WS-X6708-10GE-3C 8 8 1, 2, 3, 4, 5, 6, 7, 8

WS-X6708-10GE-3CXL 8 8 1, 2, 3, 4, 5, 6, 7, 8

To configure CoS Mutation, the following commands must be used:

Cat6500(config)# mls qos map cos-mutation testmap 3 0 2 4 1 5 7 6

Cat6500(config)# interface G1/5

Cat6500(config-if)# mls qos cos-mutation testmap

This also assumes the following commands have been assigned:

Cat6500(config)# interface G1/5

Cat6500(config-if)# switchport

Cat6500(config-if)# switchport trunk encapsulation dot1q

Cat6500(config-if)# switchport mode trunk

Cat6500(config-if)# mls qos trust trust-cos

7.8 Configure Receive Drop Thresholds

On ingress to the switch port, the frame will be placed into a receive queue. To avoid buffer overflows, the port ASIC

can implement thresholds on the receive queue and uses these thresholds to identify frames that can be dropped

once those thresholds have been exceeded. The port ASIC will use the frames set CoS value to identify which

frames can be dropped when a threshold is exceeded. This capability allows higher priority frames to remain in the

buffer for longer when congestion occurs.