CoS-markings on unconfigured switchports

[Christian Bauer]

Hello Community,

Can anybody tell me, what happens to CoS Markings of a Cisco-IP-Phone connected to a Switch (3560/29xx/...)

without any specific QoS/AutoQoS configuration on this port?

If I configure AutoQoS, the Switch will trust the markings and doesn't touch them.

I also know, that I can configure the switch to clear the markings.

But what happens if the switch is completely unconfigured for any QoS?

Thanks for Infos,

Christian

[Joseph W. Doherty · Accepted solution]

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Posting

(For most Catalyst switches) if QoS is not globally active - ingress CoS/ToS will be left as is - if QoS globally active, but port not configured to trust (the default) - ingress CoS/ToS will be reset to zero.

[Christian Bauer]

Hi Joseph,

many thanks for your fast answer. Do you have any official cisco-references regarding this behavior?

I have to present this Information to my boss and it would be great to have an official document.

Of course I searched already on cisco.com and google - and I did found a lot of configuration stuff.

But not the "non-configured"-stuff.

Many tnx,

Christian

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

I just tried to find some Cisco documentation clearly describing "no-configured", but w/o success.

PS:

BTW, if no one posts otherwise, in a day or so, that's a strong indication that what I described is correct.

[Christian Bauer]

Hi Joseph,

your statement seems to be correct. unfortunatly I also can't find any documentation about this behavior.

anyway many thanks for your help!

greets,

Chris

[krishnadas.R_2]

 With "mls qos" OFF the switch does not modify any markings.
- With "mls qos" ON the switch clears all COS, ip-prec, and DCSP, unless the trust configuration was specified.