Re: Native vlan from router to switch

"won't be able to pass any traffic"...not sure about this.
I recall seeing this in a customer's network and other vlan traffic was
passing just fine.

Ron

On Thu, Dec 8, 2011 at 11:34 AM, Narbik Kocharians <narbikk_at_gmail.com>wrote:

> Between any two switch if the Native VLAN is mismatched the trunk will come
> up but you won't be able to pass any traffic through it, and you can see
> that with a "Show spanning block".
>
> On Thu, Dec 8, 2011 at 4:31 AM, David Bass <davidbass570_at_gmail.com> wrote:
>
> > We are talking about CCIE lab, so best practice and "working" status all
> > go out the window :). In his scenario he's talking about router to
> switch
> > trunk, so no VTP or STP (if you do this switch to switch you'll
> definitely
> > have issues though, so very good to know)...CDP will definitely bark
> > non-stop though which is very irritating.
> >
> >
> >
> > On Dec 8, 2011, at 6:08 AM, Carlos G Mendioroz wrote:
> >
> > > May be depending on the equipment, the trunk will "form" just fine,
> > > if VLAN hopping is not considered to be a problem :)
> > > CDP may barf. If VLAN 1 is involved, other griefs will pop.
> > >
> > > Different problems:
> > > -framing: no problem, but "native VLAN" frames do not signal which VLAN
> > > they belong to, so if they do not match, frames will hop from one VLAN
> > > to the other.
> > >
> > > -signalling (DTP): AFAIK, VLANs are not part of the info interchanged,
> > so the trunk will form even if native is not the same.
> > >
> > > -control: (CDP/VTP/STP/...): well, you may have a problem here.
> > > In particular, CDP/VTP go on VLAN 1, so if this is one of the VLANs
> > > involved in the crossing, it won't work.
> > >
> > > -Others ?
> > >
> > > -Carlos
> > >
> > >
> > > David Bass @ 08/12/2011 08:25 -0300 dixit:
> > >> The trunk will come up fine, but you won't have IP connectivity
> between
> > the 2 devices on the VLANs/subnets you are expecting because the 2 native
> > VLANs are being bridged. Do some research on how dot1q trunks work and
> you
> > should be able to figure it out. On Dec 7, 2011, at 11:40 PM, CCIE KID <
> > eliteccie_at_gmail.com> wrote:
> > >>> Hi fellas,
> > >>>
> > >>> I tested a scenario where the Native vlan differs from the router
> port
> > to
> > >>> the switch port. I understood that if the NAtive vlan mismatches on a
> > trunk
> > >>> port , then appropriate trunking wont be formed.
> > >>> But when i connect my router to a switch and in the router
> > subinterface . I
> > >>> am having a native vlan of 20 and in the switch port it is having a
> > native
> > >>> vlan of 10 , but still the trunk is forming perfectly
> > >>>
> > >>> Can someone correct me
> > >>> fa0/1.1 fa0/1
> > >>> Router1-----------------------------------------------Switch 1
> > >>>
> > >>> Router 1
> > >>>
> > >>> inter fa 0/1.1
> > >>> encap dot1q 20 native
> > >>> ip add 10.1.1.1 255.255.255.0
> > >>> no sh
> > >>>
> > >>>
> > >>> Switch 1
> > >>>
> > >>> int fa 0/1
> > >>> enc dot1q 10 native
> > >>> swi trunk enc dot
> > >>> swi mo trunk
> > >>> no sh
> > >>>
> > >>>
> > >>> But s
> > >>>
> > >>> --
> > >>> With Warmest Regards,
> > >>>
> > >>> CCIE KID
> > >>> CCIE#29992 (Security)
> > >>>
> > >>>
> > >>> Blogs and organic groups at http://www.ccie.net
> > >>>
> > >>>
> _______________________________________________________________________
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> > > --
> > > Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina
> >
> >
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> >
> >
> >
> >
> >
> >
> >
>
>
> --
> *Narbik Kocharians
> *CCSI#30832, CCIE# 12410 (R&S, SP, Security)
> *www.MicronicsTraining.com* <http://www.micronicstraining.com/>
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Received on Thu Dec 08 2011 - 12:27:05 ART