before you understand the commands, you have to understand the queueing in 2900/3560/3750. Before I start, I assume that you know the meaning of CoS, DSCP, and IP Precedence. If not, please let me know.
For each physical port on 2900/3560/3750, there are two input queues. Each input queue has three threshold. mls qos srr-queue input maps traffic with certain CoS or DSCP value to a particular queue and threshold. For example:
mls qos srr-queue input cos-map queue 2 threshold 3 3 5
The above command maps traffic with CoS value 3 and 5 to queue 2 threshold 3.
For each physical port on 2900/3560/3750, there are four output queues. Each output queue has four threshold. mls qos srr-queue output maps traffic with certain CoS or DSCP value to a particular queue and threshold. For example:
mls qos srr-queue output dscp-map queue 1 threshold 3 40 41 42 43 44 45 46 47
The above command maps traffic with DSCP value 41 to 47 to queue 1 threshold 3.
The next question is what is a threshold. If traffic over certain threshold in a queue, the switch starts to drop traffic.
You can command mls qos queue-set output threshold to define the value of threshold. You can define two queue-set in 2900/3560/3750: queue 1 and 2. You can apply eithere queue set in the physical port.
mls qos queue-set output buffers defines the relative size of each queue.
Finally, you can define the egress queue strategy: share or shape by using commands srr-queue bandwidth share and srr-queue bandwidth shape.
The above may not be detailed enough. However, It is tough to explain everything in a message. Please read the above and ask any questions.
