set ip precedence (policy-map)
set ip precedence ip-precedence-value
no set ip precedence
ip-precedence-value A number from 0 to 7 that sets the precedence bit in the IP header.
To set the precedence value in the IP header, use the set ip precedence QoS policy-map configuration command. To leave the precedence value at the current setting, use the no form of this command.
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 following example sets the IP Precedence to 5 for packets that satisfy the match criteria of the class map called class1:Router(config)# policy-map policy1 Router(config-pmap)# class class1 Router(config-pmap-c)# set ip precedence 5
All packets that satisfy the match criteria of class1 are marked with the IP Precedence value of 5. How packets marked with the IP Precedence value of 5 are treated is determined by the network configuration.
The set ip 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" chapter of the Cisco IOS Quality of Service Solutions Configuration Guide.
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