Cisco 3750G Configuration Guide - Page 761

Chapter 33 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-precedence policy-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-dscp policy-map class configuration command. • In Cisco IOS Release 12.2(25)SE or later, if you enter or have used the set ip dscp command, the switch changes this command to set dscp in its configuration. • In Cisco IOS Release 12.2(25)SEC or later, 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. • In Cisco IOS Release 12.2(25)SED or later, 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 33-53. Note The 10-Gigabit interfaces do not support policing by using a policy map. OL-8550-02 Catalyst 3750 Switch Software Configuration Guide 33-49