Re: mls qos cos override and the likes

Emir, yes, like Adam described,

the "mls qos cos" command is the "Fallback COS" or what marking should a
packet be assigned if the switch is confused and does not know what to do.
Examples of that is that you receive untagged traffic (access port, or
native vlan on a trunk port). In case the trust would be "mls qos trust
DSCP", the setting would also apply to all non-IP traffic, like IPX, LOOP,
DTP, VTP, CDP, STP, etc.
The "mls qos cos override" command is the highest priority command, that
makes everything behave according to the set cos, no matter the
trust/service-policy settings.

The list of what takes precedence is the following:

mls qos cos override
service policy
mls qos trust
mls qos cos
Pavel

On Fri, Sep 9, 2011 at 12:16 AM, emir d souza <emir979_at_gmail.com> wrote:

> Hi Guys,
>
> I'm a bit confused with the combination of commands for mls qos on an
> interface. The objective is to mark all incoming packets on that interface
> with a cos marking of 3.
>
> What's the difference between
> interface fa0/1
> mls qos trust cos
> mls qos cos 3
>
>
> and
>
>
> interface fa0/1
> mls qos cos 3
> mls qos cos override
>
>
> and if you have both override and trust cos, which one will take
> precedence?
> Pls don't send me a Cisco link, the explanation from there is confusing.
>
>
> Cheers!
>
>
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-- 
Pavel Bykov
Blogs and organic groups at http://www.ccie.net