The root bridge, or root switch, sits at the top of the spanning tree and connects other switches in the local area network. All switches are assigned a priority value and switch ID, which is made up of the priority and MAC address. The switch with the lowest switch ID value based on these factors will be elected as the root bridge. Administrators can configure a specific switch as the root bridge by lowering its priority value below the default of 32,768.

1. Root Bridge
Or
Root Switch
www.netprotocolxpert.in

2.  A Spanning Tree is an inverted tree. The Root bridge
(switch) is a special bridge at the top of the Spanning
Tree (inverted tree).
 The branches (Ethernet connections) are then
branched out from the root switch, connecting to other
switches in the Local Area Network (LAN).
 All Bridges (Switches) are assigned a numerical value
called bridge priority.
 The Bridge (Switch) priority value is used to find the
Bridge (Switch) ID.

3.  The Switch ID is made from two values.
• The Switch Priority, which is a numerical value
defined by IEEE 802.1D, which is equal to
32,768 by default.
• The MAC Address of the Switch.

4.  If all the Switches in your Local Area Network
(LAN) are configured with the default Switch Priority
(32,768), the Switch MAC address will become the
decisive factor in electing the Root Bridge (Switch).
 The Bridge (Switch) with the lowest MAC Address is
then elected as Root Bridge (Switch).

5. If you want one
particular switch
to be the Root
Bridge (Switch),
change the
priority to a
lower value than
32,768.
Root Bridge (Switch)