TP-Link T2600G-18TSTL-SG3216 T2600G-18TSUN V1 Configuration Guide - Page 320

Configuring Spanning Tree Figure 1-2 STP/RSTP Topology Root bridge Designated port Designated port Spanning Tree Root port Designated port Root port Root port Designated port Root port Designated port Backup port Alternate port 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. Configuration Guide 290