Cisco Certified Network Professional Practice Test 2026 – Your All-in-One Guide to Exam Success!

BPDUs, or Bridge Protocol Data Units, are crucial in the Spanning Tree Protocol (STP) as they are used to manage the topology of a network by sharing information about the state of the network's switches. The primary purpose of BPDUs is indeed to advertise spanning tree information, which includes the designated port and root bridge information, as well as the path cost to the root bridge. This information is essential for switches to make informed decisions about the best paths through the network and to prevent loops by disabling redundant paths when necessary.

In this context, the other options do not align with the primary function of BPDUs. They do not manage routing updates, determine MAC addresses, nor control VLAN tagging. Rather, BPDUs focus exclusively on topology maintenance to ensure a loop-free and efficient network structure. This role is fundamental to the overall operation of Spanning Tree Protocol, allowing it to effectively manage network traffic and maintain stability within switched LANs.