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Chapter 30
Configuring QoS
These sections contain additional information about scheduling:
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Traffic Shaping
Traffic shaping is a traffic-control mechanism similar to traffic policing. While traffic policing is used
in input policy maps, traffic shaping occurs as traffic leaves an interface. The switch can apply
class-based shaping to classes of traffic leaving an interface and port shaping to all traffic leaving an
interface. Configuring a queue for traffic shaping sets the maximum bandwidth or peak information rate
(PIR) of the queue.
Note
You cannot configure traffic shaping (shape average) and CBWFQ (bandwidth) or priority queuing
(priority) for the same class in an output policy map. You cannot configure traffic shaping for a traffic
class when strict priority (priority without police) is configured for another class within the output
policy-map.
Class-Based Shaping
Class-based shaping uses the shape average policy-map class configuration command to limit the rate
of data transmission as the number of bits per second to be used for the committed information rate for
a class of traffic. The switch supports separate queues for three classes of traffic. The fourth queue is
always the default queue for class class-default, unclassified traffic.
In the Cisco ME switch, configuring traffic shaping also automatically sets the minimum bandwidth
Note
guarantee or committed information rate (CIR) of the queue to the same value as the PIR.
This example shows how to configure traffic shaping for outgoing traffic on a Fast Ethernet port so that
outclass1, outclass2, and outclass3 get a maximum of 50, 20, and 10 Mbps, respectively, of the available
port bandwidth. The class class-default gets the remaining bandwidth.
Switch(config)# policy-map out-policy
Switch(config-pmap)# class classout1
Switch(config-pmap-c)# shape average 50000000
Switch(config-pmap-c)# exit
Switch(config-pmap)# class classout2
Switch(config-pmap-c)# shape average 20000000
Switch(config-pmap-c)# exit
Switch(config-pmap)# class classout3
Switch(config-pmap-c)# shape average 10000000
Switch(config-pmap-c)# exit
Switch(config-pmap)# exit
Switch(config)# interface fastethernet 0/1
Switch(config-if)# service-policy output out-policy
Switch(config-if)# exit
78-17058-01
Traffic Shaping, page 30-19
Class-Based Weighted Fair Queuing, page 30-21
Priority Queuing, page 30-22
Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
Understanding QoS
30-19
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Troubleshooting
