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QoS on catalyst 2950 switches


I have 2 switchs C2950 that are connected trough a 10Mb link... I would like to use QoS setting that force the switchs to allow more bandwith to the packets with the DSCP field modified...

How to do so that the switchs check the ToS field and then give priority in consequence.



Re: QoS on catalyst 2950 switches

It's good to have Qos policies implemented in the 2950 . For the details regarding the configuration of QOS kindly follow the url,


Re: QoS on catalyst 2950 switches

On the 2950, you have to establish the weight of each queue based on percentage. Then you can map different cos values to different queues. For example, if you wanted a strict priority queue for VoIP traffic, you would do the following:

wrr-queue bandwidth 5 25 70 0

wrr-queue cos-map 1 1

wrr-queue cos-map 2 0

wrr-queue cos-map 3 2 3 4 6 7

wrr-queue cos-map 4 5

The first line sets the bandwidth percentage for each queue with the 4th queue set to 0 to enable it as a strict priority queue (will be exhausted first, then others will be processed). The other lines just remap the cos values (layer two) to each queue. Also keep in mind that the cos value will have an automap for the DSCP (layer 3) value. As such, CoS of 5 (automatically set by cisco phones for voice traffic) will map to a DSCP value of 40. This is not the standard as most QoS devices look for DSCP of 46 for voice traffic. You will have to use a mutation map further upstream to correct this issue. Hope this helps.

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