Class Maps; The Match Command - Cisco ME 3400 Software Configuration Manual

Chapter 33 Configuring QoS

Class Maps

As explained previously, you use an MQC class map to name a specific traffic flow (or class) and to
isolate it from all other traffic. A class map defines the criteria used to match against a specific traffic
flow to further classify it. If you have more than one type of traffic that you want to classify, you can
create another class map and use a different name. When you enter the class-map command with a
class-map name, the switch enters the class-map configuration mode. In this mode, you define the match
criterion for the traffic by using the match class-map configuration command. After a packet is matched
against the class-map criteria, it is acted on by the associated action specified in a policy map.
You can match more than one criterion for classification. You can also create a class map that requires
that all matching criteria in the class map be in the packet header by using the class map match-all
class-map name global configuration command to enter class map configuration mode.
You can configure only one match entry in a match-all class map.
Note
You can use the class map match-any class-map name global configuration command to define a
classification with any of the listed criteria.
If you do not enter match-all or match-any, the default is to match all. A match-all class map cannot
Note
have more than one classification criterion (match statement). A class map with no match condition has
a default of match all.

The match Command

To configure the type of content used to classify packets, you use the match class-map configuration
command to specify the classification criteria. If a packet matches the configured criteria, it belongs to
a specific class and is forwarded according to the specified policy. For example, you can use the match
class-map command with CoS, IP DSCP, and IP precedence values. These values are referred to as
markings on a packet. You can also match an access group, a QoS group, or a VLAN ID or ID range for
per-port, per-VLAN QoS.
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This example shows how to create a class map example to define a class that matches any of the listed
criteria. In this example, if a packet is received with the DSCP equal to 32 or a 40, the packet is identified
(classified) by the class map.
Switch(config)# class-map match-any example
Switch(config-cmap)# match ip dscp 32
Switch(config-cmap)# match ip dscp 40
Switch(config-cmap)# exit
OL-9639-07
For an input policy map, you cannot configure an IP classification (match ip dscp, match ip
precedence, match ip acl) and a non-IP classification (match cos or match mac acl) in the same
policy map or class map.
When an input policy map with only Layer 2 classification is attached to a routed port or a switch
port containing a routed switch virtual interface (SVI), the service policy acts only on switching
eligible traffic and not on routing eligible traffic.
On an 802.1Q tunnel port, you can use only an input policy map with Layer 2 classification based
on MAC ACLs to classify traffic. Input policy maps with Layer 3 classification, match Layer 2 CoS
classification, or per-port, per-VLAN policies are not supported on tunnel ports.
In an output policy map, no two class maps can have the same classification criteria, that is, the same
match qualifiers and values.
Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
Understanding QoS
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