33-25
Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-06
Chapter 33 Configuring QoS Understanding QoS
• You can use priority with the police policy-map command, or unconditional priority policing, to
reduce the bandwidth used by the priority queue. This is the only form of policing that is supported
in output policy maps. Using this combination of commands configures a maximum rate on the
priority queue, and you can use the bandwidth and shape average policy-map commands for other
classes to allocate traffic rates on other queues.
Note When priority is configured in an output policy map without the police command, you can
only configure the other queues for sharing by using the bandwidth remaining percent
policy-map command to allocate excess bandwidth.
Priority queuing has these restrictions:
• You can associate the priority command with a single unique class for all attached output polices
on the switch.
• You cannot configure priority and any other scheduling action (shape av erage or bandwidth) in the
same class.
• You cannot configure priority queuing for the class-default of an output policy map.
For more information, see the “Configuring Output Policy Maps with Class-Based Priority Queuing”
section on page 33-57.
This example shows how to configure the class out-class1 as a strict pr iority queue so that all packets in
that class are sent before any other class of traffic. Other traffic queues are configured so that out-class-2
gets 50 percent of the remaining bandwidth and out-class3 gets 20 percent of the remaining bandwidth.
The class class-default receives the remaining 30 percent with no guarantees.
Switch(config)# policy-map policy1
Switch(config-pmap)# class out-class1
Switch(config-pmap-c)# priority
Switch(config-pmap-c)# exit
Switch(config-pmap)# class out-class2
Switch(config-pmap-c)# bandwidth remaining percent 50
Switch(config-pmap-c)# exit
Switch(config-pmap)# class out-class3
Switch(config-pmap-c)# bandwidth remaining percent 20
Switch(config-pmap-c)# exit
Switch(config-pmap)# exit
Switch(config)# interface gigabitethernet 0/1
Switch(config-if)# service-policy output policy1
Switch(config-if)# exit
This example shows how to use the priority with police commands to configure out-class1 as the
priority queue, with traffic going to the queue limited to 20000000 bps so that the priority queue will
never use more than that. Traffic above that rate is dropped. The other traffic queues are configured to
use 50 and 20 percent of the bandwidth that is left, as in the previous example.
Switch(config)# policy-map policy1
Switch(config-pmap)# class out-class1
Switch(config-pmap-c)# priority
Switch(config-pmap-c)# police 200000000
Switch(config-pmap-c)# exit
Switch(config-pmap)# class out-class2
Switch(config-pmap-c)# bandwidth percent 50
Switch(config-pmap-c)# exit
Switch(config-pmap)# class out-class3
Switch(config-pmap-c)# bandwidth percent 20
Switch(config-pmap-c)# exit
Switch(config-pmap)# exit