Cisco ME 3400 Command Reference Manual page 367
Ethernet access switch
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Chapter 2 Cisco ME 3400 Ethernet Access Switch Cisco IOS Commands
Usage Guidelines
You can configure set precedence with other marking actions, specifically set cos and set qos-group,
for the same class. Support was also added for the ability to configure more than one marking action with
enhanced packet marking by using table maps for the same class.
You cannot use the set precedence command with the set dscp command to mark the same packet.
DSCP values and IP precedence values are mutually exclusive. A packet can have one value of the other,
but not both.
After precedence bits are set, other quality of service (QoS) features can then operate on the bit settings.
The network gives priority (or some type of expedited handling) to marked traffic. Typically, you set the
precedence value at the edge of the network (or administrative domain) and data is then queued
according to the precedence. Class-based weighted fair queuing (CBWFQ) can speed up handling for
high-precedence traffic at congestion points. Weighted Tail Drop (WTD) ensures that high-precedence
traffic has lower loss rates than other traffic during times of congestion.
Instead of using numeric values, you can also specify the dscp-value by using the reserved keywords EF,
AF11, and AF12.
If you are using this command to perform enhanced packet marking, you can use the from-field packet
marking option for mapping and setting the precedence value. The supported from-field marking
categories are: CoS, DSCP, and IP precedence.
If you specify a from-field category, but do not specify the table keyword and table-map-name, the
default action is to copy the value associated with the from-field category as the precedence value. For
example, if you enter the set precedence cos command, the CoS value is copied and used as the
precedence value.
Examples
This example shows how to give all FTP traffic an IP precedence value of 5:
Switch(config)# policy-map policy_ftp
Switch(config-pmap)# class ftp_class
Switch(config-pmap-c)# set precedence 5
Switch(config-pmap-c)# exit
This example shows how to assign a CoS to precedence table map to a class:
Switch(config)# policy-map inpolicy
Switch(config-pmap)# class class-default
Switch(config-pmap-c)# set precedence cos table cos-prec-tablemap
Switch(config-pmap)# exit
You can verify your settings by entering the show policy-map privileged EXEC command.
Related Commands
Command
class
policy-map
show policy-map
OL-9640-07
Description
Defines a traffic classification match criteria for the specified class-map name.
Creates or modifies a policy map that can be attached to multiple ports to
specify a service policy.
Displays QoS policy maps.
Cisco ME 3400 Ethernet Access Switch Command Reference
set precedence
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