Cisco ME 3400 Series, Software Configuration Manual

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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-07
Chapter 33 Configuring QoS
Understanding 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.
Note
You can configure only one match entry in a match-all class map.
You can use the class map match-any class-map name global configuration command to define a
classification with any of the listed criteria.
Note
If you do not enter match-all or match-any , the default is to match all. A match-all class map cannot
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.
•
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.
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