If a Switch has multiple paths to reach the Root Bridge (Switch), it must select one path and the associated port as the Root Port. Following are the different steps for selecting the Root Bridge (Switch).

• If there are two or more paths to reach the Root Bridge (Switch) select the path with the lowest accumulated path cost.

• Select the neighboring switch with the lowest Switch ID value to reach the Root Bridge (Switch).

• Select the port with the lowest Port Priority value, if you have multiple paths to reach the Root Bridge (Switch) via same neighbor switch.

• If all the ports are configured with same priority number (32 by default), select the lowest port number on the switch.

Related Topics...

• What is Broadcast Storm

• What is Layer 2 Switching loop

• What is Spanning Tree Protocol (STP)

• What is Bridge Protocol Data Unit (BPDU) frame

• Bridge Protocol Data Unit (BPDU) Frame Format

• What is a Root Bridge (Switch)

• What is a Root Port

• What are Port Cost, Port Priority and Path Cost Values

• What is a Designated Port

• How Spanning Tree Protocol (STP) select Designated Port

• Difference between Root Port and Designated Port

• Spanning Tree Port States

• Topology Changes in Spanning Tree Protocol (STP)

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• How to enable or disable Spanning Tree Protocol (STP)

• What is Rapid Spanning Tree Protocol (RSTP)

• Difference between Spanning Tree Protocol (STP) and Rapid Spanning Tree Protocol (RSTP)

• Per-VLAN Spanning Tree (PVST) and Per-VLAN Spanning Tree Plus (PVST+)