Cisco Catalyst 2960 Series, Configuration Manual

Page: 679 / 2288

Classifying, Policing, and Marking Traffic on Physical Ports by Using Policy Maps
You can configure a 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 policy map can contain a predefined 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.
• 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).
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
597
How to Configure QoS