[c-nsp] ME3400 odd DSCP bit issue

[sledge121 at gmail.com]

I think if you have both then trust overrides a policy-map rock to scissors.  It defo does on a 6500.


Sent from my iPad

On 22 May 2012, at 17:21, Sigurbjörn Birkir Lárusson<sigurbjornl at vodafone.is> wrote:

> You need to see the configuration on their side.
> 
> The switch by default will set all dscp to 0 unless trust is configured.  You can also apply a policy-map that explicitly sets the dscp to a specific value.
> 
> Kind regards,
> Sibbi
> 
> From: Lee Starnes <lee.t.starnes at gmail.com<mailto:lee.t.starnes at gmail.com>>
> To: "Sigurbjörn B. Lárusson" <sigurbjornl at vodafone.is<mailto:sigurbjornl at vodafone.is>>
> Cc: "cisco-nsp at puck.nether.net<mailto:cisco-nsp at puck.nether.net>" <cisco-nsp at puck.nether.net<mailto:cisco-nsp at puck.nether.net>>
> Subject: Re: [c-nsp] ME3400 odd DSCP bit issue
> 
> Hi Sibbi,
> 
> From what the customer tells me their switch is configured as such. The issue is not that computers marking packets does not work. That seems fine. The issue is that if the switch is the device marking the packets, we see dscp set to "0". Since we don't have access into their 3560, I can not verify how they have it setup, but I know that our ME3400 is using a policy map to set dscp dscp on all packets so that we trust what is coming in from them.
> 
> -Lee
> 
> On Mon, May 21, 2012 at 7:56 AM, Sigurbjörn Birkir Lárusson <sigurbjornl at vodafone.is<mailto:sigurbjornl at vodafone.is>> wrote:
> You need to have mls qos trust dscp on the port on the 3560 facing the
> computer, is that in place?
> 
> Kind regards,
> Sibbi
> 
> On 21.5.2012 14:42, "Lee Starnes" <lee.t.starnes at gmail.com<mailto:lee.t.starnes at gmail.com>> wrote:
> 
>> Hello all,
>> 
>> Previously I had an issue where we were stripping the dscp bits coming
>> into
>> our switch and this was solved with the policy-map that does a set dscp
>> dscp. I can send a packet from a laptop with the bits market and see these
>> bits make it all the way through our network. However, what is happening
>> is
>> our customer is setting the dscp value on their switch and not from the
>> device sending the packets. When they do this, the bits get set to 0. If
>> they disconnect their switch and connect a laptop in place of the link to
>> them from us, they see the marked packets.
>> 
>> So, my question is what causes these dscp bits to change based on the
>> customer's switch setting them and a computer setting them?
>> 
>> Computer <---> 3560 <---> ME3400 (3560 sets the dscp bit and we DON'T see
>> it.)
>> Computer <---> 3560 <---> ME3400 (computer sets the dscp bit and we DO see
>> it.)
>> 
>> Computer <---> 3560 <---> Computer (3560 sets the dscp bit and we see it.)
>> 
>> Any insight on this would be greatly appreciated.
>> 
>> Thanks,
>> 
>> -Lee
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> 
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