Re: Qos trust boundary & marking

From: Carlos G Mendioroz (tron@huapi.ba.ar)
Date: Wed Aug 27 2008 - 11:18:57 ART


That's what I thought, but even after some deep searches,
I've been unable to validate that on cisco docs.
And some material I've been shown (P4S) says otherwise.

AFAIK, you can enable DSCP pass through, but that's not default.

Thanks,
-Carlos

Bill Eyer @ 27/8/2008 08:07 -0300 dixit:
> Carlos,
>
> That's correct, when the switch receives the packet that originate in
> the PC, which the switch has marked as COS 0, it automatically marks the
> DSCP to zero. If for some reason you want a different DSCP value for
> your PC traffic, you can modify your switch's cos-dscp map.
>
> Bill
>
> Carlos G Mendioroz wrote:
>> I'm trying to nail smth:
>> Say you have
>>
>> (a) - switch - (b) - IP Phone - (c) - Pc
>>
>> And you have trust device cisco-phone at the switch.
>> 1) PC sends frame with DSCP xx (no COS cause no L@ tag),
>> 2) phone keeps DSCP and puts COS 0
>> 3) switch is trusting phone, but by default copies COS to DSCP
>>
>> so at (a) packet from PC has DSCP 0. Right ?
>
>
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-- 
Carlos G Mendioroz  <tron@huapi.ba.ar>  LW7 EQI  Argentina

Blogs and organic groups at http://www.ccie.net



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