Configuring Layer 3 Queue Limit and Drop Policies
Dropping Packets Based on IP Precedence
To drop packets based on IP precedence, enter the following commands beginning in global
configuration mode:
Command
Step 1
Router(config)# policy-map
policy-map-name
Step 2
Router(config-pmap)# class class-map-name
Step 3
PRE2
Router(config-pmap-c)# random-detect
precedence-based
PRE3
Router(config-pmap-c)# random-detect
precedence-based aggregate
[minimum-thresh min-thresh maximum-thresh
max-thresh mark-prob mark-prob]
Step 4
Router(config-pmap-c)# random-detect
precedence prec-value min-thresh-value
max-thresh-value
mark-probability-denominator-value
PRE3
Router(config-pmap-c)# random-detect
precedence values sub-class-val
[...[sub-class-val8]] minimum-thresh
min-thresh maximum-thresh max-thresh
mark-prob mark-prob
Cisco 10000 Series Router Quality of Service Configuration Guide
11-28
Purpose
Specifies the name of the policy map to be created or modified.
Enters policy-map configuration mode.
policy-map-name is the name of the policy map.
Assigns the traffic class you specify to the policy map. Enters
policy-map class configuration mode.
class-map-name is the name of a previously configured class map
and is the traffic class for which you want to define QoS actions.
Indicates that weighted random early detection (WRED) is to use
the IP precedence of a packet when calculating the packet drop
probability.
(Optional) min-thresh is the minimum number of packets allowed
in the queue. Valid minimum threshold values are from 1 to
16,384.
(Optional) max-thresh is the maximum number of packets
allowed in the queue. Valid maximum threshold values are from
the value of the minimum threshold to 16,384.
(Optional) mark-prob is the drop rate. Valid values are from 1 to
65,535. The default value is 10.
Configures WRED to drop packets based on the IP precedence
value you specify.
prec-value (PRE2) or values sub-class-val (PRE3) is a number
that identifies the IP precedence level. Valid values are from 0 to
7.
1
min-thresh is the minimum number of packets allowed in the
queue. Valid minimum threshold values are from 1 to 16,384.
max-thresh is the maximum number of packets allowed in the
queue. Valid maximum threshold values are from the value of the
minimum threshold to 16,384.
mark-probability-denominator-value (PRE2) or mark-prob
(PRE3) is the drop rate. Valid values are from 1 to 65,535. The
default value is 10.
Chapter 11
Managing Packet Queue Congestion
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