Root Bridge - TP-Link T1600G-18TS Configuration Manual

Configuring Spanning Tree
Figure 1-2 STP/RSTP Topology

Root Bridge

The root bridge is the root of a spanning tree. There is only one root bridge in each
spanning tree, and the root bridge has the lowest bridge ID.
Bridge ID
The value of the priority and MAC address of the switch. It is used to select the root bridge.
The bridge ID is composed of a 2-byte priority and a 6-byte MAC address. The priority is
allowed to be configured manually on the switch, and the switch with the lowest priority
value will be elected as the root bridge. If the priority of all the switches are the same, the
switch with the lowest MAC address is selected as the root bridge.
Port Role
 Root Port
The port selected on non-root bridges to provide the lowest root path cost. There is only
one root port in each non-root bridge.
 Designated Port
The port selected for each LAN segment to provide the lowest root path cost from that
LAN segment to the root bridge.
 Alternate Port
If a port is not selected as the designated port for it receives better BPDUs from another
switch, it will become an alternate port.
Designated port
Root port
Designated port
Root port
Designated port Backup port
Root bridge
Designated port
Root port
Designated port
Root port
Alternate port
Spanning Tree
Configuration Guide 201