Cisco 2975 - Catalyst LAN Base Switch, Руководство по настройке программного обеспечения

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Catalyst 2975 Switch Software Configuration Guide
OL-19720-02
Chapter 33 Configuring QoS
Configuring Standard QoS
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.
•
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.
•
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 ).