QoS query - 3560 switch

Unanswered Question
Jun 18th, 2008

Hi

I have a query re QoS settings on a 3560 switch. The switch has PCs and VOIP phones attached.

The 3560 is configured with what is a basically an AutoQos config. The dscp mappings, queue thresholds etc are all there in the 'sh run'. However, a 'sh mls qos queing interface f0/1' ( f0/1 is the main uplink port) returned the following:

FastEthernet0/1

Egress Priority Queue : disabled

Shaped queue weights (absolute) : 25 0 0 0

Shared queue weights : 25 25 25 25

The port bandwidth limit : 100

The port is mapped to qset : 1

This concerned me. With VOIP I would have expected the priority queue here to be enabled. It isn't. The weights are all equal too.

Can anyone tell me if this is a matter of concern - should I enable the Egress Priority Queue?

Regards

Paul

I have this problem too.
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Paolo Bevilacqua Wed, 06/18/2008 - 04:44

Hi, to be honest with you, there is never to be concerned about QoS on an ethernet switch.

Whatever way you set it, and whatever it reports, voice will work just fine and you will have no issues. To all effects, time spent configuring QoS on a switch, is better spent doing something else.

I understand that what I say is not canonical, but if you don't believe me, go ahead and try :)

Personally, I wouldn't leave AUTOQOS on. I would disable it. We've seen many instances where it shutting it off "fixes" issues. Plus, some earlier IOS versions had the WRONG dscp mappings. The SRND actually does a good job of showing you access ports, uplinks, phone ports, Call Center agents, softphone, etc. with configurations for each. Of course with some of the 2960 switches the policing options aren't as granular as the 3560's and higher switches.

Again if you aren't running into congestion issues, queueing won't even come into play. Its also preferable to mark the traffic as close to the source as possible.

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