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24-8
Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
Chapter 24 Configuring QoS
Understanding QoS
These sections contain additional information about classification:
• “Class Maps” section on page 24-8
• “The match Command” section on page 24-8
• “Classification Based on Layer 2 CoS” section on page 24-9
• “Classification Based on IP Precedence” section on page 24-9
• “Classification Based on IP DSCP” section on page 24-9
• “Classification Comparisons” section on page 24-10
• “Classification Based on QoS Groups” section on page 24-11
• “Classification Based on VLAN IDs” section on page 24-12
Class Maps
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
wish to classify more than one type of traffic, you can create another class map and use a different name.
When you use the class-map command with a class-map name, the router 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, 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.
• 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.
• In an output policy map, no two class maps can have the same classification criteria, that is, the same
match qualifiers and values.