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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
Chapter 1 Configuring QoS
Configuring Standard QoS
A policy map also has these characteristics:
• A policy map can contain multiple class statements, each with different match criteria and policers.
• A policy map can contain a pre-defined default traffic class explicitly placed at the end of the map.
• A separate policy-map class can exist for each type of traffic received through a port.
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.
• 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 the “Classifying, Policing, and Marking Traffic on SVIs
by Using Hierarchical Policy Maps” section on page 1-63.
• A policy-map and a port trust state can both run on a physical interface. The policy-map is applied before
the port trust state.
• When you configure a default traffic class by using the class class-default policy-map configuration
command, unclassified traffic (traffic that does not meet the match criteria specified in the traffic
classes) is treated as the default traffic class (class-default).
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