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Cisco MWR 2941 Mobile Wireless Edge Router Release 3.5 Command Reference, Cisco IOS Release 15.1(3)MR

OL-26895-01

Chapter Cisco MWR 2941 Router Command Reference, Release 15.1(3)MR

set precedence

Precedence Value

The network gives priority (or some type of expedited handling) to marked traffic through the application

of WFQ or WRED at points downstream in the network. Typically, you set the precedence value at the

edge of the network (or administrative domain); data then is queued according to the specified

precedence. WFQ can speed up handling for certain precedence traffic at congestion points. WRED can

ensure that certain precedence traffic has lower loss rates than other traffic during times of congestion.

The set precedence command cannot be used with the set dscp command to mark the same packet. The

two values, differentiated services code point (DSCP) and precedence, are mutually exclusive. A packet

can have one value or the other, but not both.

Using This Command with the Enhanced Packet Marking Feature

If you are using this command as part of the Enhanced Packet Marking feature, you can use this

command to specify the “from-field” packet-marking category to be used for mapping and setting the

precedence value. The “from-field” packet-marking categories are as follows:

• CoS

• QoS group

If you specify a “from-field” category but do not specify the table keyword and the applicable

table-map-name argument, the default action will be to copy the value associated with the “from-field”

category as the precedence value. For instance, if you configure the set precedence cos command, the

CoS value will be copied and used as the precedence value.

You can do the same for the QoS group-marking category. That is, you can configure the set precedence

qos-group command, and the QoS group value will be copied and used as the precedence value.

The valid value range for the precedence value is a number from 0 to 7. The valid value range for the

QoS group is a number from 0 to 99. Therefore, when configuring the set precedence qos-group

command, note the following points:

• If a QoS group value falls within both value ranges (for example, 6), the packet-marking value will

be copied and the packets will be marked.

• If QoS group value exceeds the precedence range (for example, 10), the packet-marking value will

not be copied, and the packet will not be marked. No action is taken.

Setting Precedence Values for IPv4 Packets Only

To set the precedence values for IPv4 packets only, use a command involving the ip keyword like the

match ip precedence or match ip dscp command or include the match protocol ip command along

with the others in the class map. Without the additional ip keyword, the class-map may match both IPv6

and IPv4 packets (depending on the other match criteria) and the set precedence or set dscp command

may act upon both types of packets.

Examples The following example shows how to use the set precedence command.

Router(config)# policy-map policy-cos

Router(config-pmap)# class class-default

Router(config-pmap-c)# set precedence 4

Router(config-pmap-c)# end

The set precedence command is applied when you create a service policy in QoS policy-map

configuration mode. This service policy is not yet attached to an interface or to an ATM virtual circuit.

For information on attaching a service policy to an interface, refer to the “Modular Quality of Service

Command-Line Interface Overview” chapter of the Cisco IOS Quality of Service Solutions

Configuration Guide.

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