Configuring The Egress Expedite Queue - Cisco Catalyst 3550 series Software Configuration Manual

Configuring Standard QoS
Command
Step 8 show running-config
or
show mls qos interface interface-id
queueing
Step 9
show mls qos interface buffers
Step 10 copy running-config startup-config
To disable WRED, use the no wrr-queue 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.

Configuring the Egress Expedite Queue

You can ensure that certain packets have priority over all others by queuing them in the egress expedite
queue. WRR services this queue until it is empty before servicing the other queues.
Beginning in privileged EXEC mode, follow these steps to enable the egress expedite queue:
Command
Step 1 configure terminal
Step 2 mls qos
Step 3
interface interface-id
Catalyst 3550 Multilayer Switch Software Configuration Guide
29-62
Purpose
Verify the DSCP-to-threshold map.
Verify the thresholds.
(Optional) Save your entries in the configuration file.
Purpose
Enter global configuration mode.
Enable QoS on the switch.
Enter interface configuration mode, and specify the egress
Gigabit-capable Ethernet interface.
Chapter 29 Configuring QoS
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