in pvst, there is seperate spanning tree for each vlan
there 3 switches
sw0 , sw1 and sw2
vlan 1, vlan 2 and vlan 3
i have enable pvst for each vlan
for vlan 1 , sw2 is the root bridge
now for vlan 2 the bid of switches will remain same as it was in vlan 1 or it going to change
because i think in pvst there is seperate spanning tree fro each vlan
so for vlan 2 and vlan 3 how root bridge election will happen
The bid should be the same. Therefore if you want different root bridges you need to tweak the priority to a lower value on the switch that you want to become the root for a particular VLAN.
the guidance is don't let the root bridge elect itself; you want the root switch to be the hub of the switched network, and on a switch that is optimally placed in the network... likewise, with per vlan, force all vlans on the root switch to be root as well... makes sense to me... keep it simple with spanning tree; it is THE loop free mechanism for layer 2... you are the administrator of your world...
Yes you are right arteq unless you use hsrp and load balancing. VLan 1 and 2 on one access switch, second switch -HSRP Avtive (backup for vlan 2) and root bridge for vlan 1( secondary root for vlan 2)and you have third switch HSRP Avtive for vlan 2 ( backup for vlan 1) and root bridge for vlan 2 ( secondary for vlan 1).
But that is different story.