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Testing QOS settings


I have spent a bit of time trying to generate enough traffic to test allocating bandwidth among egress queues on a a fa port on a 3550 switch.

We have a requirement to limit the traffic over a metro ethernet LAN between two specific devices to 6mb ( of the available 10mb), during times of congestion only! So I have decided to mark this traffic with dscp and leave all else as best effort. Then I have allocated 40 % of egress queue 1 to best effort general traffic and 60% for queue 2 mapped to relevant dscp value. Queues 3 and 4 are not used.

I have an ftp server running and two hosts connecting and also a basic traffic generator to test.......but cannot get taffic to go over 9.8 or 9.9 mb.I have used the bandwidth statement( is no good for this...we need to be confident of what is happening before we can use this config. I would very much appreciate any tips you may have.


  • WAN Routing and Switching

Re: Testing QOS settings


for testing ONLY: shutdown spanning tree and create a loop. Create some broadcasts (f.e. ping to trigger ARP) - this should overload the link easily. Your prioritized traffic should get through, i.e. the download should start nevertheless and get some bandwidth.

Turn ON spanning tree after testing!

Second option: get some freeware tool like UDP flodder, which creates IP packets at a defined rate to overload the link.

Hope this helps! Please rate all posts.

Regards, Martin

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