From: kevin gannon (kevin@gannons.net)
Date: Tue Oct 25 2005 - 15:47:14 GMT-3
Is PSVT not carried in the native VLAN only so mixing/killing them
could result in loops:
http://www.cisco.com/univercd/cc/td/doc/product/lan/c2900xl/29_35xp/eescg/masctrnk.htm#xtocid262862
Regards
Kevin
On 10/25/05, Gustavo Novais <gustavo.novais@novabase.pt> wrote:
> Hi
>
> One question concerning switching.
>
> if you have a 802.1q trunk joining two different VTP domains (SW1-VTP
> domain A-------------802.1q trunk---------------SW2-VTP domain B), you
> must have (allow) matching vlans on both ends of the trunk.
>
> So you will have VTPA-vlan1---- VTPB-vlan1, VTPA-vlan50----VTPB-vlan50
> and so on. Besides that each switch has its own PVST+ database (meaning
> that on switch 1 has N stp instances and switch 2 has P stp instances.
>
> What will happen if by mistake on SW1 side we change the trunk's native
> vlan to a vlan that does not exist on VTP B, meaning that there is no
> STP instance on SW2 for that vlan?
>
> I tried to replicate that situation, and the result was that no traffic
> would pass though any trunk, even those that didn't interconnect SW1 to
> SW2, I'm still trying to figure out what could have happened... For what
> I could see there was no spanning-tree change or recomputation.
>
> I know that at GS, we try to understand how to make things work, and
> how, but at this case I'm trying to understand how things should not
> work!
>
> Any thoughts?
>
> Thanks
>
> Gustavo
>
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