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Configuring Precedence Classification
The Cisco Nexus 2148 Fabric Extender does not support frames with the dot1p vlan 0 tag.
Note
If a system class is configured with a no-drop function, the match cos command serves an additional purpose.
The switch sends the CoS value to the adapter so that the adapter will apply a PFC pause for this CoS value.
The FCoE system class has a default CoS value of 3. You can add a match cos configuration to the FCoE
system class to set a different CoS value. A PFC pause will be applied to traffic that matches the new value.
Procedure
Step 1
Step 2
Step 3
Step 4
This example shows how to classify traffic by matching packets based on a defined CoS value:
switch# configure terminal
switch(config)# class-map type qos match-any class_cos
switch(config-cmap-qos)# match cos 4, 5-6
Use the show class-map command to display the CoS value class-map configuration:
switch# show class-map class_cos
Configuring Precedence Classification
You can classify traffic based on the precedence value in the type of service (ToS) byte field of the IP header
(either IPv4 or IPv6). The following table shows the precedence values:
Table 3: Precedence Values
Value
<0-7>
Cisco Nexus 5000 NX-OS Quality of Service Configuration Guide, Release 5.1(3)N2(1)
10
Command or Action
switch# configure terminal
switch(config)# class-map type
qos class-name
switch(config-cmap-qos)# match
cos cos-value
switch(config-cmap-qos)# no
match cos cos-value
Purpose
Enters global configuration mode.
Creates a named object that represents a class of traffic.
Class-map names can contain alphabetic, hyphen, or
underscore characters, are case sensitive, and can be up to 40
characters.
Specifies the CoS value to match for classifying packets into
this class. You can configure a CoS value in the range of 0
to 7.
When a Cisco Nexus 2148T Fabric Extender is
Note
connected and in use, data traffic should never be
marked with a CoS value of 7. CoS 7 is reserved for
control traffic transiting the Fabric Extender.
(Optional)
Removes the match from the traffic class.
List of Precedence Values
IP precedence value
Configuring Classification
OL-26657-01
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