Re: VLAN based QoS

Well, what Eseosa is saying is certainly true. However, you don't
HAVE to trust anything. If the task did not state to trust DSCP I
don't see a reason to have that statement there. If you mark DSCP for
one class of traffic (say HTTP) that does not imply that you MUST
trust DSCP for everything else.

Also, don't forget to apply "mls qos vlan-based" on your interfaces : )

On Thu, May 13, 2010 at 8:18 AM, hopalong <ccieangel2_at_googlemail.com> wrote:
> Thank you, so if you change the dscp for one type of traffic, you have to
> have the trust statement for the class default. OK, but still not
> understanding why that should be true when you have defined the only traffic
> you want to change? Any idea or just one of those cisco things?!
>
> On Thu, May 13, 2010 at 12:46 PM, eseosa <eseosa.ehiwe_at_gmail.com> wrote:
>
>> Yes, trust dscp implies that you are trusting the dscp marking "on
>> any traffic coming from any device on that vlan (i.e class
>> class-default) " but for http traffic coming from any webserver on
>> that vlan you are overriding or setting the dscp marking to what you
>> have specified.
>>
>>
>> HTH
>>
>>
>>
>> On 5/13/10, hopalong <ccieangel2_at_googlemail.com> wrote:
>> > Hi
>> >
>> > I am configuring VLAN based QoS on a catalyst switch.
>> >
>> > I have matched the traffic thus:
>> >
>> > ip access-list extended HTTP
>> > permit tcp any eq 80 any
>> > !
>> > class-map HTTP
>> > match access-group name HTTP
>> >
>> > and then I need to change the dscp value:
>> >
>> > policy-map VLAN46
>> > class HTTP
>> > set dscp 16
>> >
>> > and then apply:
>> >
>> > interface vlan 46
>> > service-policy input VLAN46
>> >
>> > My question is that the solution provided has an additional line in the
>> > class-map HTTP which reads:-
>> >
>> > class class-default
>> > trust dscp
>> >
>> > is this strictly necessary to the solution ?
>> > Thanks for reading!
>> >
>> >
>> > Blogs and organic groups at http://www.ccie.net
>> >
>> > _______________________________________________________________________
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>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>>
>>
>> --
>> Warm Regards,
>>
>> Eseosa
>> CCIE #23782
>> Before God we are all equally wise - and equally foolish.
>> Albert Einstein
>
>
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> _______________________________________________________________________
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