Auto-QoS on Catalyst 2950

[Kevin Dorrell]

I have been looking at the way auto-qos behaves on a 2950 switch. Now, it used to be that the weightings given to the four WRR queues was 20 1 80 0. This made sense to me because it made a strict priority out of queue 4, which is the one that will get all my DSCP EF (i.e. voice) traffic.

I did this on a switch with version 12.1(22)EA4, and I see that the default weightings are now 10 20 70 1. This does not seem to make sense to me at all, and looks like the worst possible combination for voice. It is giving the least weighting to queue 4, which is the one carrying the voice traffic.

Is this a bug, or is there some reasoning behind it?

BTW, this is a duplicate posting. It was originally posted on the Infrastructure section, but I got no response there.

Kevin Dorrell

Luxembourg

[Aaron Harrison]

Looks wrong to me too - just looked at the manual, which states that to enable strict priority you set the weight to 0.

Also in the manual:

"For example, if one queue has a weight of 3 and another has a weight of 4, three packets are sent from the first queue for every four that are sent from the second queue."

So in theory with the config it's given you this means that 70 packets of video in queue 3 would be sent per 1 packet of voice.

Aaron

[Kevin Dorrell]

Thanks Aaron. I was having a look at the config guide, and that confirms that they really do give only 1% bandwidth (actually 1/101) and no priority to the EF voice queue. Extraordinary!

http://www.cisco.com/en/US/products/hw/switches/ps628/products_configuration_guide_chapter09186a00802c31e8.html#wp1125449

Thanks at least for answering my posting - I didn't get any responses at all from the other version of it.

Kevin Dorrell

Luxembourg