Which spanning-tree port role receives the best BPDU toward the root bridge on a nonroot switch?

Answer choices

Why each option matters

Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.

Technical deep dive

How to think about this question

Spanning Tree Protocol (STP) is a Layer 2 network protocol that prevents loops in Ethernet networks by creating a loop-free logical topology. STP elects a root bridge and then determines the best path from every switch to this root bridge. Each non-root switch selects a single port, called the root port, which provides the lowest cost path back to the root bridge. This root port is the primary forwarding port toward the root and receives the best Bridge Protocol Data Units (BPDUs) from the root bridge. The root port is chosen based on the lowest path cost to the root bridge, which is calculated by summing the costs of all links between the switch and the root. This port role is critical because it forwards traffic toward the root bridge and receives superior BPDUs compared to other ports. Designated ports forward traffic away from the root on a segment, alternate ports serve as backup paths, and disabled ports do not participate in forwarding or BPDU exchange. A common exam trap is confusing the root port with the designated or alternate ports. While designated ports forward traffic away from the root and alternate ports provide backup paths, only the root port receives the best BPDU toward the root bridge on a non-root switch. Understanding this distinction is essential for correctly answering STP questions and for practical network troubleshooting and design.

More questions from this exam

Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.

FAQ

Questions learners often ask