Cisco Enterprise Network Core Technologies (ENCOR) Practice Exam 2026 - Free ENCOR Practice Questions and Study Guide

The selection of the root bridge in Spanning Tree Protocol (STP) is conducted through a process that prioritizes certain criteria, with the primary goal of maintaining a loop-free topology in Ethernet networks. The correct answer highlights that STP utilizes the lowest bridge priority followed by the lowest MAC address when determining which bridge will serve as the root bridge.

STP assigns a priority value (the default value is 32768) to each switch in the network. When the switches participate in the Bridge Protocol Data Unit (BPDU) exchange, they compare their priority values. The switch with the lowest priority becomes the root bridge. If multiple switches share the same priority, STP further assesses their MAC addresses, with the switch that has the lowest MAC address being chosen as the root bridge.

This two-step selection process ensures a uniform methodology for identifying the root bridge, which is critical as the root bridge serves as the reference point for all spanning tree calculations, helping to maintain a stable and efficient network.

By focusing on the lowest priority and the lowest MAC address, STP optimizes the selection process to prevent conflicts and ensure stability in the network topology.