Cisco Catalyst 3750 Software Configuration Manual page 574

Configuring Hierarchical QoS
discards or marks packets destined for a queue when that queue is congested. It discards packets fairly
and before the queue is full. Packets with high IP-precedence values are preferred over packets with low
IP-precedence values. If you want to enable DSCP-based WRED instead of IP precedence-based WRED,
see the
Before beginning this procedure, make sure that you have reviewed the configuration guidelines and
have created the class map to isolate traffic. For more information, see the
Configuration Guidelines" section on page 26-76
Maps" section on page
CBWFQ and Tail Drop" section on page
Beginning in privileged EXEC mode, follow these steps to configure class-level CBWFQ and IP
precedence-based WRED in a service policy for outbound traffic. This procedure is optional. The
examples that follow the procedure show how to configure class-level and VLAN-level CBWFQ and IP
precedence-based WRED.
Command
Step 1 configure terminal
Step 2
policy-map policy-map-name
Step 3
class class-name
Step 4 bandwidth {bandwidth-kbps | percent
percent}
Step 5
random-detect precedence-based
Catalyst 3750 Metro Switch Software Configuration Guide
26-94
"Configuring CBWFQ and DSCP-Based WRED" section on page 26-89
26-78. For information on how to configure tail drop, see the
Purpose
Enter global configuration mode.
Create a policy map by entering the policy-map name, and enter
policy-map configuration mode.
By default, no policy maps are defined.
Specify the name of the class whose traffic policy you want to create
or change, and enter policy-map class configuration mode.
By default, no traffic classes are defined.
Specify the minimum bandwidth provided to a class belonging to the
egress policy-map when there is traffic congestion in the switch. If the
switch is not congested, the class receives more bandwidth than you
specify with the bandwidth command.
CBWFQ derives the weight for packets belonging to the class from the
bandwidth allocated to the class. CBWFQ then uses the weight to
ensure that the queue for the class is serviced fairly.
By default, no bandwidth is specified.
You can specify the bandwidth in kbps or as a percentage:
•
•
Specify all the class bandwidths in either kbps or in percentages, but
not a mix of both. The amount of bandwidth configured should be large
enough to accommodate Layer 2 overhead.
Enable IP precedence-based WRED as a drop policy. By default,
WRED is disabled.
and the "Classifying Egress Traffic by Using Class
26-86.
For bandwidth-kbps, specify the bandwidth amount in kbps
assigned to the class. The range is 200 to 2000000. Allocate the
bandwidth in 100-kbps increments; otherwise, the software rounds
down the bandwidth to the nearest 100-kbps increment.
For percent percent, specify the percentage of available
bandwidth assigned to the class. The range is 1 to 100. The sum of
the class bandwidth percentages within a single policy map cannot
exceed 99 percent. Percentage calculations are based on the
bandwidth available at the parent class (or the physical level if it
is the parent).
Chapter 26 Configuring QoS
"Hierarchical QoS
"Configuring
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