Class-Based Weighted Fair Queuing - Cisco ME 3400 Software Configuration Manual
Ethernet access switch
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Chapter 33
Configuring QoS
The total of the minimum bandwidth guarantees (CIR) for each queue of the child policy cannot exceed
Note
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.
When you configure bandwidth in a policy map, you must configure all rates in the same format, either
Note
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.
•
•
For more information, see the
section on page
OL-9639-07
When you use the bandwidth policy-map class configuration command to configure a class of
traffic as an absolute rate (kilobits per second) or a percentage of total bandwidth, this represents
the minimum bandwidth guarantee (CIR) for that traffic class. This means that the traffic class gets
at least the bandwidth indicated by the command, but is not limited to that bandwidth. Any excess
bandwidth on the port is allocated to each class in the same ratio in which the CIR rates are
configured.
You cannot configure bandwidth as an absolute rate or a percentage of total bandwidth when
Note
strict priority (priority without police) is configured for another class in the output policy.
When you use the bandwidth policy-map class configuration command to configure a class of
traffic as a percentage of remaining bandwidth, this represents the portion of the excess bandwidth
of the port that is allocated to the class. This means that the class is allocated bandwidth only if there
is excess bandwidth on the port, and if there is no minimum bandwidth guarantee for this traffic
class.
You can configure bandwidth as percentage of remaining bandwidth only when strict
Note
priority (priority without police) is configured for another class in the output policy map.
"Configuring Output Policy Maps with Class-Based-Weighted-Queuing"
33-54.
Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
Understanding QoS
33-23
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