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set cos
The match cos and set cos commands can be used together to allow routers and switches to interoperate
and provide quality of service (QoS) based on the CoS markings.
Layer 2 to Layer 3 mapping can be configured by matching on the CoS value because switches already
can match and set CoS values. If a packet that needs to be marked to differentiate user-defined QoS
services is leaving a router and entering a switch, the router should set the CoS value of the packet
because the switch can process the Layer 2 header.
Using This Command with the Enhanced Packet Marking Feature
You can use this command as part of the Enhanced Packet Marking feature to specify the "from-field"
packet-marking category to be used for mapping and setting the CoS value. The "from-field"
packet-marking categories are as follows:
•
•
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 CoS value. For instance, if you configure the set cos precedence command, the
precedence value will be copied and used as the CoS value.
You can do the same for the DSCP marking category. That is, you can configure the set cos dscp
command, and the DSCP value will be copied and used as the CoS value.
Note
If you configure the set cos dscp command, only the first three bits (the class selector bits) of the DSCP
field are used.
Examples
In the following example, the policy map called "cos-set" is created to assign different CoS values for
different types of traffic. This example assumes that the class maps called "voice" and "video-data" have
already been created.
Router(config)# policy-map cos-set
Router(config-pmap)# class voice
Router(config-pmap-c)# set cos 1
Router(config-pmap-c)# exit
Router(config-pmap)# class video-data
Router(config-pmap-c)# set cos 2
Router(config-pmap-c)# end
Enhanced Packet Marking Example
In the following example, the policy map called "policy-cos" is created to use the values defined in a
table map called "table-map1". The table map called "table-map1" was created earlier with the
table-map (value mapping) command. For more information about the table-map (value mapping)
command, see the table-map (value mapping) command page.
In this example, the setting of the CoS value is based on the precedence value defined in "table-map1":
Router(config)# policy-map policy-cos
Router(config-pmap)# class class-default
Router(config-pmap-c)# set cos precedence table table-map1
Router(config-pmap-c)# end
Cisco MWR 2941 Router Command Reference, Release 15.0(1)MR
406
Precedence
Differentiated services code point (DSCP)
Cisco MWR 2941 Router Command Reference, Release 15.0(1)MR
OL-23890-01
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