Rate Shaping on Cisco 3560

Unanswered Question
Nov 3rd, 2008

I have a Cisco 3560, with egress of 3M. I have two connections - one going to video equipment, the other going to firewall. When video equipment is being used i want 80% on the 3M to be used for that purpose. When video is not used, i want all BW to be applied to Internet connection. Please help.

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Joseph W. Doherty Tue, 11/04/2008 - 06:03

I don't have a 3560/3750 in front of me at the moment, so I can't provide an exact example (also config might differ depending what IOS level you're running).

In general, the 3560/3750 offers four hardware egress queues per physical interface. What you want to do is map your video traffic into one queue and all other traffic into another queue. Additionally, you'll specify that your queues share bandwidth but in the proportions you desire, 80/20 (default is equal sharing).

(NB: when video traffic isn't using its bandwidth, available bandwidth will be provided to the other queue.)

For the egress queues to function, you'll also need to insure you limit the physical outbound port to 3 Mbps. This is best accomplished by setting the port to 10 Mbps and then setting active usage to 30% (less might be needed since port active % usage is not precise).

Mapping taffic into queues can be a bit confusing, although there are also defaults. Hopefully, video device might be able to pre-mark its packets (best if you can select marking value).

You might also have to enable mls QoS for these feature to become active. Detailed information, for all of this, can be found in the configuration guide's QoS chapter for your IOS version.


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