Cisco Systems 3560 Classifying, Policing, and Marking Traffic on Physical Ports by Using Policy Maps

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Catalyst 3560 Switch Software Configuration Guide
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Chapter 34 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 34-52.
• Beginning with Cisco IOS Release 12.2(40)SE, 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.