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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 20 Configuring QoS
Configuring QoS
To disable WRED, use the no wrr random-detect max-threshold [queue-id] interface configuration
command. To return to the default DSCP-to-threshold map, use the no wrr-queue dscp-map
[threshold-id] interface configuration command.
This example shows how to configure the WRED queue threshold values for queue 1 to 50 percent
and 100 percent, for queue 2 to 70 percent and 100 percent, for queue 3 to 50 percent and 100 percent,
and for queue 4 to 70 percent and 100 percent on the egress interface (Gigabit Ethernet 0/1). The ingress
interface (Gigabit Ethernet 0/2) is configured to trust the DSCP in the incoming packets, to map DSCPs
0, 8, 16, 24, 32, 40, 48, and 56 to threshold 1, and to map DSCPs 10, 20, 30, 40, 50, and 60 to threshold 2.
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# wrr-queue random-detect max-threshold 1 50 100
Switch(config-if)# wrr-queue random-detect max-threshold 2 70 100
Switch(config-if)# wrr-queue random-detect max-threshold 3 50 100
Switch(config-if)# wrr-queue random-detect max-threshold 4 70 100
Switch(config-if)# exit
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# mls qos trust dscp
Switch(config-if)# wrr-queue dscp-map 1 0 8 16 24 32 40 48 56
Switch(config-if)# wrr-queue dscp-map 2 10 20 30 40 50 60
As a result of this configuration, when the queues 1 and 3 are filled above 50 percent, packets with
DSCPs 0, 8, 16, 24, 32, 40, 48, and 56 are randomly dropped. The same packets are randomly dropped
when queues 2 and 4 are filled above 70 percent. When the second threshold (100 percent) is exceeded,
all queues randomly drop packets with DSCPs 10, 20, 30, 40, 50, and 60.
Step 4
wrr-queue random-detect
max-threshold queue-id
threshold-percentage1
threshold-percentage2
Configure WRED drop threshold percentages on each egress queue.
The default, WRED is disabled, and no thresholds are configured.
•
For queue-id, specify the ID of the egress queue. The range is 1
to 4, where queue 4 can be configured as the expedite queue. For
more information, see the
“Configuring the Egress Expedite
Queue” section on page 20-50
.
•
For threshold-percentage1 threshold-percentage2, specify the
threshold percentage values. Separate each value with a space. The
range is 1 to 100.
Step 5
exit
Return to global configuration mode.
Step 6
interface interface-id
Enter interface configuration mode, and specify the ingress
Gigabit-capable Ethernet interface.
Step 7
wrr-queue dscp-map threshold-id dscp1
... dscp8
Map DSCP values to the WRED drop thresholds of the egress queues.
By default, all DSCP values are mapped to threshold 1.
•
For threshold-id, specify the threshold ID of the queue. The range
is 1 to 2.
•
For dscp1 ... dscp8, specify the DSCP values that are mapped to the
threshold ID. Enter up to eight DSCP values per command.
Separate each value with a space. The range is 0 to 63.
Step 8
show running-config
Verify the DSCP-to-threshold map.
Step 9
show mls qos interface buffers
Verify the thresholds.
Step 10
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Command
Purpose
