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Software Configuration Guide—Release 12.2(25)SG
OL-7659-03
Chapter 27 Configuring Quality of Service
Configuring QoS
This example shows how to configure the DSCP 5 as the default on Fast Ethernet interface 5/24:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface fastethernet 5/24
Switch(config-if)# qos dscp 5
Switch(config-if)# end
Switch#
This example shows how to verify the configuration:
Switch# show qos interface fastethernet 6/1
QoS is enabled globally
Port QoS is enabled
Port Trust State:CoS
Default DSCP:0 Default CoS:0
Tx-Queue Bandwidth ShapeRate Priority QueueSize
(bps) (bps) (packets)
1 31250000 disabled N/A 240
2 31250000 disabled N/A 240
3 31250000 disabled normal 240
4 31250000 disabled N/A 240
Switch#
Configuring Transmit Queues
The following sections describes how to configure the transmit queues:
• Mapping DSCP Values to Specific Transmit Queues, page 27-48
• Allocating Bandwidth Among Transmit Queues, page 27-49
• Configuring Traffic Shaping of Transmit Queues, page 27-50
• Configuring a High Priority Transmit Queue, page 27-50
Depending on the complexity of your network and your QoS solution, you might need to perform all of
the procedures in the next sections, but first you will need to make decisions about these characteristics:
• Which packets are assigned (by DSCP value) to each queue?
• What is the size of a transmit queue relative to other queues for a given port?
• How much of the available bandwidth is allotted to each queue?
• What is the maximum rate and burst of traffic that can be transmitted out of each transmit queue?
Mapping DSCP Values to Specific Transmit Queues
To map the DSCP values to a transmit queue, perform this task:
Command Purpose
Step 1
Switch(config)# [no] qos map dscp
dscp-values
to
tx-queue
queue-id
Maps the DSCP values to the transit queue. dscp-list can
contain up 8 DSCP values. The queue-id can range from
1 to 4.
Use the no qos map dscp to tx-queue command to clear
the DSCP values from the transit queue.