Cisco Nexus 5000 Series Switch CLI Software Configuration Guide, NX-OS 4.0(1a)N1 (OL-16597-01, January 2009)

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31-9
Cisco Nexus 5000 Series Switch CLI Software Configuration Guide
OL-16597-01
Chapter 31 Configuring QoS
Configuring System Classes
To disable link-level flow control, perform this task:
Configuring System Classes
This section describes how to configure system classes on the switch. The steps to configure a system
class are described in the following topics:
• Configuring Class Maps, page 31-9
• Configuring Policy Maps, page 31-10
• Creating the System Service Policy, page 31-11
• System Class Example, page 31-11
• Enabling Jumbo MTU, page 31-12
• Verifying Jumbo MTU, page 31-12
Configuring Class Maps
The class-map command creates a named object that represents a class of traffic. In the class map, you
specify a set of match criteria for classifying the packets. For system classes, the only match criteria
supported is match cos.
If a system class is configured with 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 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. PFC Pause will be applied to traffic that matches the new value.
To configure a class map for a system class, perform this task:
Command Purpose
switch(config-if)# no flowcontrol
[receive {on|off}] [transmit {on|off}]
Disables 802.3x link-level flow control for the
selected interface.
Command Purpose
Step 1
switch# configure terminal
Enters configuration mode.
Step 2
switch(config)# class-map name
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.
Step 3
switch(config-cmap)# match cos cos-value
Specifies the CoS value to match for classifying
packets into this class. You can configure a CoS value
in the range of 1 to 7.
Note CoS value 0 is reserved for the default drop
system class (class-default).