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Configuring QoS
Understanding QoS
You can optionally include keywords to evaluate these match commands by entering class-map match-any or
class-map match-all. If you specify match-any, the traffic being evaluated must match one of the specified criteria.
If you specify match-all, the traffic being evaluated must match all of the specified criteria. A match-all class map
can contain only one match statement, but a match-any class map can contain multiple match statements.
If you do not enter match-all or match-any, the default is to match all.
You use the match class-map configuration commands to specify criteria for classifying packets. If a packet matches
the specified criteria, that packet is considered a member of the class and is forwarded according to the QoS
specifications set in the traffic policy. Packets that fail to meet any of the matching criteria are classified as members
of the default traffic class.
2.
Create a traffic policy to associate the traffic class with one or more QoS features.
You use the policy-map policy-map-name global configuration command to create a traffic policy and to enter
policy-map configuration mode. A traffic policy defines the QoS features to associate with the specified traffic class. A
traffic policy contains three elements: a name, a traffic class (specified with the class policy-map configuration
command), and the QoS policies configured in the class.
You name the traffic policy in the policy-map command line to enter policy-map configuration mode.
In policy-map configuration mode, enter the name of the traffic class used to classify traffic to the specified policy,
and enter policy-map class configuration mode.
In policy-map class configuration mode, you can enter the QoS features to apply to the classified traffic. These
include using the set, police, or police aggregate commands for input policy maps or the bandwidth, priority,
queue-limit or shape average commands for output policy maps.
Note:
A packet can match only one traffic class within a traffic policy. If a packet matches more than one traffic class in
the traffic policy, the first traffic class defined in the policy is used. To configure more than one match criterion for
packets, you can associate multiple traffic classes with a single traffic policy.
3.
Attach the traffic policy to an interface.
You use the service-policy interface configuration command to attach the policy map to an interface for packets entering
or leaving the interface. You must specify whether the traffic policy characteristics should be applied to incoming or
outgoing packets. For example, entering the service-policy output class1 interface configuration command attaches
all the characteristics of the traffic policy named class1 to the specified interface. All packets leaving the specified
interface are evaluated according to the criteria specified in the traffic policy named class1.
Input and Output Policies
Policy maps are either input policy maps or output policy maps, attached to packets as they enter or leave the switch by
service policies applied to interfaces. Input policy maps perform policing and marking on received traffic. Policed packets
can be dropped or reduced in priority (marked down) if they exceed the maximum permitted rates. Output policy maps
perform scheduling and queuing on traffic as it leaves the switch.
Input policies and output policies have the same basic structure; the difference is in the characteristics that they regulate.
Figure 77 on page 574
You can configure a maximum of 256 policy maps.
The number of configurable policer profiles on the switch is 256. The number of supported policer instances on the
switch is 1024 minus 1 more than the number of interfaces on the switch. On a 24-port switch, the number of available
policer instances is 999. You can use a policer profile in multiple instances.
You can apply one input policy map and one output policy map to an interface.
shows the relationship of input and output policies.
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