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Cisco ASR 901 Aggregation Services Router Command Reference Guide
OL-26031-07
Chapter 1 CLI Command Reference
set cos
set cos
To set the Layer 2 class of service (CoS) value of an outgoing packet, use the set cos command in
policy-map class configuration mode. To remove a specific CoS value setting, use the no form of this
command.
set cos {cos-value}
no set cos {cos-value}
Syntax Description
Command Default No CoS value is set for the outgoing packet.
Command Modes Policy-map class configuration
Command History
Usage Guidelines CoS packet marking is supported only in the Cisco Express Forwarding switching path.
The set cos command should be used by a router if a user wants to mark a packet that is being sent to a
switch. Switches can leverage Layer 2 header information, including a CoS value marking.
The set cos command can be used only in service policies that are attached in the output direction of an
interface. Packets entering an interface cannot be set with a CoS value.
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:
• Precedence
• Differentiated services code point (DSCP)
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.
cos-value Specific IEEE 802.1Q CoS value from 0 to 7.
Release Modification
15.1(2)SNG Support for this command was introduced on the Cisco ASR 901 router.
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