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Weighted fair queue question

when i configure WFQ on an interface, i see a parameter called available bandwidth on the sh interface command which is less than the actual interface bandwidth. And if the traffic exceeds the available bandwidth then will result in output queue drops.

also i found that changing the interface bandwidth to any arbitrary value changes these parameters as well. ( eg. if i ahve a 1 MB interface and i configure the bandwidht statement as 10 MB, the available bandwidth shows around 8MB) . will it mean then, it will not show drops till the traffic exceeds 8 MB.

please make me understand how this is calculated and how does it affect the interface parameters like queuing etc.

5 REPLIES
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Re: Weighted fair queue question

WFQ will always alocate the same bandwidth to each flow, irrespective of what kind of flows they are. This is the typical behavior of flow based WFQ. The behavior is similar to plain FQ since the flows are all of equal weights

Try this URL:http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_configuration_guide_chapter09186a00800b75af.html

Re: Weighted fair queue question

Hello,

in case you use WFQ configured on an interface, the configured "bandwidth" has no influence on the queueing behaviour. Software based queueing (like WFQ in a router) will be involved, when the hardware queue is full, i.e. when there is more traffic than the interface can send at the time. You can never send more traffic than the layer1 clock rate allows you to send - no matter what you configure with the interface command "bandwidth".

In case you configure CBWFQ through a policy-map, then the configured interface "bandwidth" is used to calculate the bandwidth per class within percent based CBWFQ. Again this will only make sense if you adjust the interface "bandwidth" to the clock rate.

Hope tis helps! Please rate all posts.

Regards, Martin

Community Member

Re: Weighted fair queue question

OK - So you're saying that since I'm using WFQ, the badwidth command does nothing? So what do I need to do to get it working? I tried setting the "bandwidth percent" to 20 and it still does the same thing (no marked outgoing packets)... And why is it working on my other router with the same config?

I also tried configuring a policy map, but when I apply it to the interface, it won't even match traffic.

Thanks for your response!

Re: Weighted fair queue question

Hello,

could you explain exactly what you are trying to achieve?

You could try to lead you in the correct direction.

are you trying to policy a traffic? or shape it?

what configurations are you using?

Vlad

Community Member

Re: Weighted fair queue question

http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.1ddb1479

Check this message for details. I don't know why a new thread was started...

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