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Configuring QoS
QoS Treatment for Performance-Monitoring Protocols
This example shows how to configure a policy map that shapes a port to 90 Mbps, allocated according to the out-policy
policy map configured in the previous example. The service-policy policy map class command is used to create a child
policy to the parent:
Switch(config)# policy-map out-policy-parent
Switch(config-pmap)# class class-default
Switch(config-pmap-c)# shape average 90000000
Switch(config-pmap-c)# service-policy out-policy
Switch(config-pmap-c)# exit
Switch(config-pmap)# exit
Switch(config)# interface fastethernet0/1
Switch(config-if)# service-policy output out-policy-parent
Switch(config-if)# exit
Parent-Child Hierarchy
The switch also supports parent policy levels and child policy levels for traffic shaping. The QoS parent-child structure
is used for specific purposes where a child policy is referenced in a parent policy to provide additional control of a
specific traffic type.
The first policy level, the parent level, is used for port shaping, and you can specific only one class of type class-default
within the policy. This is an example of a parent-level policy map:
Switch(config)# policy-map parent
Switch(config-pmap)# class class-default
Switch(config-pmap-c)# shape average 50000000
Switch(config-pmap-c)# exit
The second policy level, the child level, is used to control a specific traffic stream or class, as in this example:
Switch(config)# policy-map child
Switch(config-pmap)# class class1
Switch(config-pmap-c)# priority
Switch(config-pmap-c)# exit
Note: The total of the minimum bandwidth guarantees (CIR) for each queue of the child policy cannot exceed the total
port-shape rate.
This is an example of a parent-child configuration:
Switch(config)# policy-map parent
Switch(config-pmap)# class class-default
Switch(config-pmap-c)# shape average 50000000
Switch(config-pmap-c)# service-policy child
Switch(config-pmap-c)# exit
Switch(config-pmap)# exit
Switch(config)# interface fastethernet0/1
Switch(config-if)# service-policy output parent
Switch(config-if)# exit
Class-Based Weighted Fair Queuing
You can configure class-based weighted fair queuing (CBWFQ) to set the relative precedence of a queue by allocating
a portion of the total bandwidth that is available for the port. You use the bandwidth policy-map class configuration
command to set the output bandwidth for a class of traffic as a rate (kilobits per second), a percentage of total
bandwidth, or a percentage of remaining bandwidth.
Note: When you configure bandwidth in a policy map, you must configure all rates in the same format, either a configured
rate or a percentage. The total of the minimum bandwidth guarantees (CIR) for each queue of the policy cannot exceed
the total speed of the parent.
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