ROOT BRIDGE AND ROOT ID

In this article ,I will explain the  concept of root id and how we can choose the root bridge.


Choose the Root Bridge:


1) Each Switch has a bridge ID (BID) of priority value fallowed by MAC address.
             Bridge ID= combination of priority + MAC address
2) Switches exchange bridge protocol data units (BPDU) to compare bridge ids.
3)  The switch with the lowest bridge id become the root bridge.
4) Administrator can set the priority to fix the selection.


Bridge ID:

• The bridge id consist of bridge priority,extended system id, and MAC address.
• By default the priority is 32768.
• Lowest priority wins.
• Value 1------65536,multiples of 40960.
• Extended system id identifies VLAN.
• MAC address used,if priority is same.Better not to rely on MAC address.