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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter20 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 thresh ol d val ues for q ueu e 1 to 5 0 pe rcen t
and 100 percent, for queue 2 to 70 percent and 100 percent, for qu eu e 3 to 50 per cent an d 10 0 p er cent ,
and for queue 4 to 70 percent and 100 percent on the e gress 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 packet s are rando mly d rop pe d
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, 5 0, a nd 60.
Step4 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 conf igur ed .
•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.
Step5 exit Return to global configuration mode.
Step6 interface interface-id Enter interface configuration mode, and specify the ingress
Gigabit-capable Ethernet interface.
Step7 wrr-queue dscp-map threshold-id dscp1
... dscp8 Map DSCP values to the WRED drop thresholds of the eg ress 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.
Step8 show running-config Verify the DSCP-to-threshold map.
Step9 show mls qos interface buffers Verify the thresholds.
Step10 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose