2
I know what you are thinking.. Wait a minute if the Mac address is part of the First Criteria (Bridge ID) why would you need any other criteria, they all should be unique, right?
Let’s Recall what a MAC address is:
98 : FA : 9B : 53 : BA : 9F
The ID of the Company who Made it
The Serial Number of the NIC
So you just bought 20 of these from the same vendor, how different are they
98 : FA : 9B : 53 : BA : 01
98 : FA : 9B : 53 : BA : 02
98 : FA : 9B : 53 : BA : 03
You also decided to use VLAN 1, VLAN 2, VLAN 3 etc, and used the default Priority
VLAN 1
VLAN 2
VLAN 3
In each case you are adding 4 to the default priority and all 3 have the same BID