Solved: multiple spanning tree solution

hasnaoukarim · ‎08-31-2012

hello everyone, please I give you a scenario and you answer me if it will work or not thank you :).

i have 2 switche connected with 3 fastethernet (FE1, FE2 and FE3) in 2 sides

I created two vlans and I declare these 2 vlans as follows:

vlan1 and vlans 2 to fe1

vlan1 to Fe2

vlan2 to Fe3

I configure in the two switches MSTP and I map the 2vlans (vlans1 and vlans2) to one instance (instance 1),

knowing that the two switches are in the same regions.

there are two loops here

the first is in the vlan 1 between FE1 and FE2

the second is between the vlan 2 fe1 and Fe3

will MSTP detect a loop? will MSTP work well ?

excuse my english because i'm french speaker thank you

krahmani323 · ‎08-31-2012

Hello Karim and Alessio !

From the initial description there is two instances => Instance 0 (or IST) where all vlans are mapped by default & Instance 1 which vlans 1 & 2 have been mapped to.

As MSTP works on an instance basis (and not on a single vlan basis) it will compute based on instances 0 and 1.

The BPDUs will be exchanged on the three Fe interfaces (note the BDPUs for both instances will be exchanged through a “centralized” IST BPDU containing inf