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How to verify QOS

Christoph Zach
Occasional Contributor

How to verify QOS

Hi all

We have set up QOS with DSCP
How can i verify correct operation of qos on the switches ?
Matt Hobbs
Honored Contributor

Re: How to verify QOS

Hi Christoph,

With the 5300 and 2600's, there's no real commands (that I know of) on the switches that you can use to verify that it is definitely doing what you've set. You can do the 'show qos' commands and 'show bandwidth' but they don't tell you anything other than what you have set on the swtiches already.

In regards to checking 802.1p tags, I posted this for someone else asking a similar question a few months ago:
The only way I know to check if the priority tags are being inserted, is to perform a packet capture with ethereal.

One way is to put a hub in between two switches, and connect your ethereal machine into the hub. You can also set a mirror-port on your switch. That port will need to be a tagged member of the VLAN you are interested in. I would then monitor the uplink port. Sometimes the hub is just easier...

Next, depending on your NIC you may not be able to see the VLAN tag if using Windows. If you have an Intel or Broadcom NIC though you're in luck - http://wiki.ethereal.com/CaptureSetup/VLAN

Otherwise I've found if you run Ethereal on Linux you can always see the tag.

DSCP is much easier to check since it's in the layer 3 header, you simply need to do a regular packet capture and check that the DSCP code has been inserted.

Probably the most simple way to test QoS is to do a real life test, make a VoIP call and start copying a large file over the same link, or something like that. If the call sounds good you know you've been successful.

Otherwise there are professional tools such as Ixia Chariot.

Hope this helps.


Mohieddin Kharnoub
Honored Contributor

Re: How to verify QOS


I think its easy to Check QoS Setup and verify it,
But its Difficult to verify QoS operation except under Congestion.

I believe that Networkers have a "Seventh Sense :)" , i mean under congestion, they can know, if they really have a converged Network with QoS implemented.

Ethereal for DSCP is also a good Idea, anyway you can verify your implementation of QoS from the switch CLI it self, but functionality and operation, i think Monitoring the most Congested time.

Good Luck!!!
Science for Everyone
Sergej Gurenko
Trusted Contributor

Re: How to verify QOS

If you start kicking HP Presales and PostSales forces. They are declaring collecting demands and feedback from the users. There is a chances that they will introduce some QoS monitoring commands one day
But the truth is that such commands are very asic specific if there was not designed in the ASIC there will no possibility to introduce such commands in software.
Same story with Cisco 3550/3560-3750. The new generation 3560-3750 have broader CoS/DSCP monitoring features than older 3550.

P.S. The slogan of Procurve is "We are not doing the best switches. We are doing good enough"

Re: How to verify QOS

If you have verified the tags in the header with Ethereal, you can actually do real world tests with a bandwidth killer tool. Solarwinds has a 30 day trial that comes with a "WAN Killer" app. It allows you to do a DOS attack against a machine. You can send 100% utilization ie 100mb, 1000mb etc across your network with it then place a voice call, if the call is not getting jitter, etc than it is working.