Cisco 4500 Sup-6 QoS configuration

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Sep 10th, 2008
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Was surprized to find out that 12.2(46)SG has MQC QoS, so no mor LAN QoS.

Very good, long time awaiting ...

QoS configuration page for 45oo Sup-6 is very simplistic and does not really open up the differences between long existing MQC on routers and MQC on 4500 Sup-6.

For example trying to configure a standard policy with LLQ where Priority and Bandwith statements are needed to support real-time and data traffic.

policy-map Policy-1


priority xx

Priority command does not have any further arguments, so cannot configure the speed stament.

OK, trying to configure Policer with speed option, but the next class does not accept bandwith statements

... very frustrating when QoS configuration page states "Please reffer to MQC configuration page"

It looks different obviously, but no documentation support to find out whete are those differences.

Any help ?????

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Overall Rating: 5 (1 ratings)
t814687 Thu, 09/11/2008 - 07:26
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Igor, I guess you went through the config guide and it says there when the "bandwidth remaining" command becomes available in the config for the class. Also you can try police xx command in the class for priority traffic Hope this helps.

config will look something like this:

policy-map Policy-1



police conform-action transmit

Priority queuing

On Supervisor Engine 6-E only one transmit queue on a port can be configured as strict priority (termed Low Latency Queue, or LLQ).

LLQ provides strict-priority queuing for a traffic class. It enables delay-sensitive data, such as voice, to be sent before packets in other queues. The priority queue is serviced first until it is empty or until it is under its shape rate. Only one traffic stream can be destined for the priority queue per class-level policy. You enable the priority queue for a traffic class with the priority policy-map class configuration command at the class mode.

A LLQ can starve other queues unless it is rate limited. Supervisor Engine 6-E does not support conditional policing where a 2-parameter policer (rate, burst) becomes effective when the queue is congested (based on queue length). However, it supports application of an unconditional policer to rate limit packets enqueued to the strict priority queue.

When a priority queue is configured on one class of a policy map, only bandwidth remaining is accepted on other classes, guaranteeing a minimum bandwidth for other classes from the remaining bandwidth of what is left after using the priority queue. When a priority queue is configured with a policer, then either bandwidth or bandwidth remaining is accepted on other classes.

Surya ARBY Mon, 09/09/2013 - 02:41
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I will hijack this thread

Regarding QOS on SUP6 / SUP7 with MQC :

I want to limit the bandwidth allocated to a priority queue, is it possible to use the shape mode instead of an explicit policer ?

I want to limit the allocated bandwidth of the PQ as a percentage of the link as defined in current QOS best practices (30%)

but the config provided (unlimited PQ) is not accurate with the QOS model defined above in the previous link


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