What must occur for a Designated Port to be elected?

For a Designated Port to be elected in a spanning tree topology, it is essential for that port to have the lowest Bridge ID among the remaining ports on a segment. The Designated Port is responsible for forwarding packets towards the root bridge from a specific network segment, and the election process is designed to ensure that the most efficient and reliable path is chosen.

In this process, when evaluating which port will serve as the Designated Port, the decision is based on the Bridge ID, which is a combination of the bridge priority and the MAC address. The port with the lowest Bridge ID indicates the bridge with the highest priority or the lowest MAC address on that segment, ensuring that the traffic flow is directed efficiently and effectively.

Other factors are considered later when determining the port states, but the election of the Designated Port focuses primarily on the lowest Bridge ID among competing ports on the same network segment. Therefore, the correct choice highlights the fundamental principle by which the spanning tree protocol operates to achieve loop-free topologies in Ethernet networks.