Simulating WAN connections in a lab

Unanswered Question
Aug 4th, 2009

I need to setup a test lab at work to simulate parts of our production environment.

I need to have 4 links running at 256K. I wanted to setup 4 routers so i could apply some QoS traffic shaping but have been told all i have to work with is 1 Cisco 3560.

So looks like all i can do is setup rate-limiting, but i have not have much experience with it. So is it possible to use the rate-limiting features on the VLAN interfaces to limit the traffic on those VLANS down to a 256K link?

So i have something like this:

Interface Vlan20

rate-limit input 2000000 1500 2000 conform-action transmit exceed-action drop

Would this accomplish what I'm trying to achieve?

thanks

I have this problem too.
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Joseph W. Doherty Wed, 08/05/2009 - 03:42

No, since a rate-limiter or policer will drop the excess packets, not queue them.

On a 3560, you might use the srr-queue bandwidth limit command to "shape" the port, although it won't support 256 Kbps, I believe. You might also consider using srr-queue bandwidth shape command.

PS:

A 3560's QoS feature support is quite different and less rich vs. an ISR, so unsure how much benefit you'll derive.

Peter Paluch Wed, 08/05/2009 - 03:58

Hello,

I agree. Moreover, even when you shape your link to a certain bandwidth, the link itself will still work at, say, 100Mbps and all frames will be transmitted at this rate. This will distort your delay measurements, as the 256 Kbps link has its transmission delay over 390 times higher than the 100 Mbps.

Best regards,

Peter

LucaSalvatore_2 Wed, 08/05/2009 - 14:57

Thanks for the replies guys. I have actually sorted it out using the srr-queue bandwidth limit command.

I hard coded the port to be a 10Mb port, then used the command 'srr-queue bandwidth limit 10' command. This drops the speed down to 512Kb which is as low as i can get.

I was after 256Kb but 512 will be sufficient for the lab.

thanks!

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