Cisco Certified Network Professional Practice Test 2025 – Your All-in-One Guide to Exam Success!

The configuration of a root bridge is correctly described by stating that a bridge with the lowest bridge ID is elected as the root. In the Spanning Tree Protocol (STP), the root bridge serves as the central reference point for all other switches in the network topology. Each switch has a unique bridge ID that consists of the bridge priority (a configurable value) combined with the MAC address of the switch.

When switches in the network compute which will be the root bridge, they exchange Bridge Protocol Data Units (BPDUs) that contain this bridge ID. The switch with the lowest bridge ID is selected as the root bridge. If two switches have the same bridge priority, the tie is broken using the MAC address, with the lower MAC address winning.

This process helps to ensure a loop-free topology in Ethernet networks, which is critical for efficient data transmission. Therefore, this selection process for the root bridge is foundational to the operation of STP.