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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
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Chapter 39 Configuring QoS Configuring Standard QoS
Beginning in privileged EXEC mode, follow these steps to configure the priority queue. This procedure
is optional.
To return to the default setting, use the no mls qos srr-queue input priority-queue queue-id global
configuration command. To disable priority queueing, set the bandwidth weight to 0, for example, mls
qos srr-queue input priority-queue queue-id bandwidth 0.
This example shows how to assign the ingress bandwidths to the queues. Queue 1 is the priority queue
with 10 percent of the bandwidth allocated to it. The bandwidth ratios allocated to queues 1 and 2 is
4/(4+4). SRR services queue 1 (the priority queue) first for its configured 10 percent bandwidth. Then
SRR equally shares the remaining 90 percent of the bandwidth between queues 1 and 2 by allocating 45
percent to each queue:
Switch(config)# mls qos srr-queue input priority-queue 1 bandwidth 10
Switch(config)# mls qos srr-queue input bandwidth 4 4
Configuring Egress Queue Characteristics
Depending on the complexity of your network and your QoS solution, you might need to perform all of
the tasks in the next sections. You will need to make decisions about these characteristics:
• Which packets are mapped by DSCP or CoS value to each queue and threshold ID?
• What drop percentage thresholds apply to the queue-set (four egress queues per port), and how much
reserved and maximum memory is needed for the traffic type?
• How much of the fixed buffer space is allocated to the queue-set?
• Does the bandwidth of the port need to be rate limited?
• How often should the egress queues be serviced and which technique (shaped, shared, or both)
should be used?
Command Purpose
Step 1 configure terminal Enter global configuration mode.
Step 2 mls qos srr-queue input
priority-queue queue-id bandwidth
weight
Assign a queue as the priority queue and guarantee bandwidth on the stack
or internal ring if the ring is congested.
By default, the priority queue is queue 2, and 10 percent of the bandwidth
is allocated to it.
• For queue-id, the range is 1 to 2.
• For bandwidth weight, assign the bandwidth percentage of the stack
or internal ring. The range is 0 to 40. The amount of bandwidth that
can be guaranteed is restricted because a large value affects the entire
ring and can degrade the switch or stack performance.
Step 3 end Return to privileged EXEC mode.
Step 4 show mls qos interface queueing
or
show mls qos input-queue
Verify your entries.
Step 5 copy running-config startup-config (Optional) Save your entries in the configuration file.