Cisco Catalyst 3750 Metro Command Reference Manual page 319

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Catalyst 3750 Metro Switch Cisco IOS Commands

Usage Guidelines

Use the mls qos queue-set output qset-id buffers global configuration command to allocate a fixed

number of buffers to the four queues in a queue-set.

The drop-threshold percentages can exceed 100 percent and can be up to the maximum (if the maximum

threshold exceeds 100 percent).

The egress queue-set default settings are suitable for most situations. You should change them only when

you have a thorough understanding of the queues and if these settings do not meet your QoS solution.

The switch uses a buffer allocation scheme to reserve a minimum amount of buffers for each egress

queue-set, to prevent any queue or port from consuming all the buffers and depriving other queues, and

to control whether to grant buffer space to a requesting queue. The switch detects whether or not the

target queue has consumed more buffers than its reserved amount (under-limit), whether it has consumed

all of its maximum buffers (over-limit), and whether the common pool is empty (no free buffers) or not

empty (free buffers). If the queue is not over-limit, the switch can allocate buffer space from the reserved

pool or from the common pool (if it is not empty). If there are no free buffers in the common pool or if

the queue is over-limit, the switch drops the frame.

This example shows how to map a port to queue-set 2. It configures the drop thresholds for queue 2 to

40 and 60 percent of the allocated memory, guarantees (reserves) 100 percent of the allocated memory,

and configures 200 percent as the maximum memory that this queue can have before packets are

Switch(config)# mls qos queue-set output 2 threshold 2 40 60 100 200

Switch(config)# interface fastethernet1/0/1

Switch(config-if)# queue-set 2

You can verify your settings by entering the show mls qos interface [interface-id] buffers or the show

mls qos queue-set privileged EXEC command.

Related Commands

mls qos queue-set output buffers

show mls qos interface

show mls qos queue-set

Allocates buffers to a queue-set.

Maps a port to a queue-set.

Displays buffer allocation information.

Displays settings for the queue-set.

mls qos queue-set output threshold

Catalyst 3750 Metro Switch Command Reference