Configuring Srr Shared Weights On Egress Queues - Cisco WS-C3560-48PS-S Software Configuration Manual
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Configuring Standard QoS
Configuring SRR Shared Weights on Egress Queues
In shared mode, the queues share the bandwidth among them according to the configured weights. The
bandwidth is guaranteed at this level but not limited to it. For example, if a queue empties and does not
require a share of the link, the remaining queues can expand into the unused bandwidth and share it
among them. With sharing, the ratio of the weights controls the frequency of dequeuing; the absolute
values are meaningless.
Note
The egress queue default settings are suitable for most situations. You should change them only when
you have a thorough understanding of the egress queues and if these settings do not meet your QoS
solution.
Beginning in privileged EXEC mode, follow these steps to assign the shared weights and to enable
bandwidth sharing on the four egress queues mapped to a port. This procedure is optional.
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3
srr-queue bandwidth share weight1
weight2 weight3 weight4
Step 4
end
Step 5
show mls qos interface interface-id
queueing
Step 6
copy running-config startup-config
To return to the default setting, use the no srr-queue bandwidth share interface configuration
command.
This example shows how to configure the weight ratio of the SRR scheduler running on an egress port.
Four queues are used, and the bandwidth ratio allocated for each queue in shared mode is 1/(1+2+3+4),
2/(1+2+3+4), 3/(1+2+3+4), and 4/(1+2+3+4), which is 10 percent, 20 percent, 30 percent, and 40
percent for queues 1, 2, 3, and 4. This means that queue 4 has four times the bandwidth of queue 1, twice
the bandwidth of queue 2, and one-and-a-third times the bandwidth of queue 3.
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# srr-queue bandwidth share 1 2 3 4
Catalyst 3560 Switch Software Configuration Guide
28-62
Purpose
Enter global configuration mode.
Specify the port of the outbound traffic, and enter interface configuration
mode.
Assign SRR weights to the egress queues.
By default, all four weights are 25 (1/4 of the bandwidth is allocated to
each queue).
For weight1 weight2 weight3 weight4, enter the weights to control the
ratio of the frequency in which the SRR scheduler sends packets. Separate
each value with a space. The range is 1 to 255.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Chapter 28
Configuring QoS
78-16156-01
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