Cisco Systems 3750E manual 36-51

Chapter 36 Configuring QoS

Configuring Standard QoS

Classifying, Policing, and Marking Traffic on Physical Ports by Using Policy Maps

You can configure a nonhierarchical policy map on a physical port that specifies which traffic class to act on. Actions can include trusting the CoS, DSCP, or IP precedence values in the traffic class; setting a specific DSCP or IP precedence value in the traffic class; and specifying the traffic bandwidth limitations for each matched traffic class (policer) and the action to take when the traffic is out of profile (marking).

A policy map also has these characteristics:

•A policy map can contain multiple class statements, each with different match criteria and policers.

•A separate policy-map class can exist for each type of traffic received through a port.

•A policy-map trust state and a port trust state are mutually exclusive, and whichever is configured last takes affect.

Follow these guidelines when configuring policy maps on physical ports:

•You can attach only one policy map per ingress port.

•If you configure the IP-precedence-to-DSCP map by using the mls qos map ip-prec-dscp

dscp1...dscp8 global configuration command, the settings only affect packets on ingress interfaces that are configured to trust the IP precedence value. In a policy map, if you set the packet IP precedence value to a new value by using the set ip precedence new-precedencepolicy-map class configuration command, the egress DSCP value is not affected by the IP-precedence-to-DSCP map. If you want the egress DSCP value to be different than the ingress value, use the set dscp new-dscppolicy-map class configuration command.

•If you enter or have used the set ip dscp command, the switch changes this command to set dscp in its configuration.

•You can use the set ip precedence or the set precedence policy-map class configuration command to change the packet IP precedence value. This setting appears as set ip precedence in the switch configuration.

•You can configure a separate second-level policy map for each class defined for the port. The second-level policy map specifies the police action to take for each traffic class. For information on configuring a hierarchical policy map, see Classifying, Policing, and Marking Traffic on SVIs by Using Hierarchical Policy Maps, page 36-55.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02		36-51