Quality of Service (QoS): Managing Bandwidth More Effectively

Using QoS Classifiers To Configure Quality of Service for Outbound Traffic

Note On Changing a Priority Setting

If a QoS classifier is using a policy (codepoint and associated priority) in the DSCP Policy table, you must delete or change this usage before you can change the priority setting on the codepoint. Otherwise the switch blocks the change and displays this message:

Cannot modify DSCP Policy < codepoint > - in use by other qos rules.

In this case, use show qos < classifier > to identify the specific classifiers using the policy you want to change; that is:

show qos device-priority show qos port-priority

show qos tcp-udp-port-priority show qos vlan-priority

show qos type-of-service

Note that protocol-priority is not included because a DSCP policy is not meaningful for this classifier and therefore not configurable in this case.

For example, suppose that the 000001 codepoint has a priority of 6, and several classifiers use the 000001 codepoint to assign a priority to their respective types of traffic. If you wanted to change the priority of codepoint 000001 you would do the following:

1.Identify which QoS classifiers use the codepoint.

2.Change the classifier configurations by assigning them to a different DSCP policy, or to an 802.1p priority, or to No-override.

3.Reconfigure the desired priority for the 000001 codepoint.

4.Either reassign the classifiers to the 00001 codepoint policy or leave them as they were after step 2, above.

Example of Changing the Priority Setting on a Policy When

One or More Classifiers Are Currently Using the Policy

Suppose that codepoint 000001 is in use by one or more classifiers. If you try to change its priority, you see a result similar to the following:

Figure 15-32. Example of Trying To Change the Priority on a Policy In Use by aClassifier

In this case, you would use steps similar to the following to change the priority.

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