TP-Link T1500-28PCT T1500-28PCTTL-SL2428PUN V3 User Guide - Page 322
Root Bridge, Bridge ID, Port Role, Designated Port
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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. The switch with te lowest bridge ID will be the root bridge, and there is only one root bridge in a spanning tree. Bridge ID Bridge ID is used to select the root bridge. It 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 the switches are the same, the switch with the smallest MAC address will be selected as the root bridge. Port Role ■■ Root Port The root port is selected on non-root bridge that can provide the lowest root path cost. There is only one root port in each non-root bridge. ■■ Designated Port The designated port is selected in each LAN segment that can 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. User Guide 299
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