Command:

set ip precedence (route-map)


Mode:

Router(config-route-map)#


Syntax:

set ip precedence [number | name]
no set ip precedence

 

Syntax Description:

number | name (Optional) A number or name that sets the precedence bits in the IP header. The values for the number argument and the corresponding name argument are listed in the table below, from least to most important.

 

Command Description:

To set the precedence value (and an optional IP number or IP name) in the IP header, use the set ip precedence route-map configuration command. To leave the precedence value unchanged, use the no form of this command.

Number and Name Values for IP Precedence

Nameroutinepriorityimmediateflashflash-overridecriticalinternetnetwork
Number
0
1
2
3
4
5
6
7

You can set the precedence using either a number or the corresponding name. Once the IP Precedence bits are set, other QoS services such as weighted fair queueing (WFQ) and Weighted Random Early Detection (WRED) then operate on the bit settings.

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 IP Precedence at the edge of the network (or administrative domain); data then is queued based on the 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 mapping from arguments such as routine and priority to a precedence value is useful only in some instances. That is, the use of the precedence bit is evolving. You can define the meaning of a precedence value by enabling other features that use the value. In the case of the high-end Internet QoS available from Cisco, IP Precedences can be used to establish classes of service that do not necessarily correspond numerically to better or worse handling in the network.

Use the route-map (IP) global configuration command with the match and set route-map configuration commands to define the conditions for redistributing routes from one routing protocol into another, or for policy routing. Each route-map command has an associated list of match and set commands. The match commands specify the match criteria--the conditions under which redistribution or policy routing is allowed for the current route-map command. The set commands specify the set actions--the particular redistribution or policy routing actions to perform if the criteria enforced by the match commands are met. The no route-map command deletes the route map.

The set route-map configuration commands specify the redistribution set actions to be performed when all of the match criteria of a route map are met.


Example:

The following example sets the IP Precedence to 5 (critical) for packets that pass the route map match:

Router(config)# interface serial 0
Router(config-if)# ip policy route-map texas

Router(config)# route-map texas
Router(config-route-map)# match length 68 128
Router(config-route-map)# set ip precedence 5


Misconceptions:

None


Related Commands:

fair-queue
ip policy route-map
route-map

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