Summary

• The number and capabilities of queues on Catalyst switches depend upon the model of the switch, supervisor, and line cards. PQ and WRR are the two queuing methods used for Catalyst switches. The use of PQ can starve lower-priority queues.

• With WRR, different weights are assigned to each queue. Use of WRR scheduling prevents the low-priority queues from being completely neglected during periods of high-priority traffic. On most Catalyst switches, a single priority queue can be configured with WRR to ensure priority dispatch of voice traffic.

• To configure CoS-to-queue mappings for PQ on the Catalyst 2950 switch, specify the queue ID of the CoS priority queue. (Ranges are 1 to 4 where 1 is the lowest CoS priority queue.) Then, specify the CoS values that are mapped to the queue ID. Use the wrr-queue cos-map quid cos1...cosn command.

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