From: Gustavo Novais (gustavo.novais@novabase.pt)
Date: Tue Oct 25 2005 - 12:26:40 GMT-3
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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