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New Member

priority-queue and SRR

All, I want to make sure on something in particular. I have, on a 3750, shaped round robin QoS in place. "mls qos" with cos-dscp mappings, thresholds, etc. On the interfaces, I have srr.... shape and srr.... share commands, and have recently put in "priority-queue" command on an interface, hoping that it will put in place a priority queue. My question is this: Do you have to have policy-maps in place on a 3750 for the "priority-queue output" interface command to work, or will "priority-queue output" work with SRR?

1 ACCEPTED SOLUTION

Accepted Solutions
Super Bronze

Re: priority-queue and SRR

Hi Joseph

Yes - that's correct...

What Chris is saying though is that QoS on the 3750 doesn't follow the normal MQC routines of defining a policy map and applying it on an outbound interface...

Whilst policy maps can be defined they are NOT what controls queueing - this is always the SRR mechanism as it's a hardware platform feature.

Policy maps are typically used to control classification on these boxes - based on this classification, traffic is admitted to an SRR queue.

Regards

Aaron

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Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!
6 REPLIES
Super Bronze

Re: priority-queue and SRR

Hi

It works with SRR - basically with SRR you have four queues - the priority-queue out command makes one work as an LLQ (all traffic serviced from this queue before any other queue).

Once enabled, the priority-queue is queue 1 so any SRR settings you put in for Q1 are ignored when working out the sharing or shaping.

Regards

Aaron

Please rate helpful posts.

Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!
New Member

Re: priority-queue and SRR

But the main thing I want to know is that you dont have to have a policy-map in place to use priority-queue, correct?

Hall of Fame Super Silver

Re: priority-queue and SRR

As AAron stated SRR priority-queue out commad on a switch acts similar to policy-map command on a router, there is no policy-map output avaialble on the switch.

Chris

New Member

Re: priority-queue and SRR

Actually cderen, the 3750 is a layer 3 switch, and you can do class maps/policy maps on it. I just wanted to make sure that the "priority-queue out" command works with SRR and WITHOUT a policy-map in place on the 3750. Is that correct?

Super Bronze

Re: priority-queue and SRR

Hi Joseph

Yes - that's correct...

What Chris is saying though is that QoS on the 3750 doesn't follow the normal MQC routines of defining a policy map and applying it on an outbound interface...

Whilst policy maps can be defined they are NOT what controls queueing - this is always the SRR mechanism as it's a hardware platform feature.

Policy maps are typically used to control classification on these boxes - based on this classification, traffic is admitted to an SRR queue.

Regards

Aaron

Please rate helpful posts.

Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!
New Member

Re: priority-queue and SRR

Thanks, much clearer. I apprecaite the both of you.

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