Cisco Certified Network Associate (CCNA) Practice Exam

Which methods does spanning tree use when electing a designated port?

1. All ports transition to blocking while the election of the designated port takes place

2. If necessary, designated port election ties are broken by upstream root cost path

3. Root ports and designated ports transition to the forwarding state

4. When a stable spanning-tree state is reached, BPDUs are transmitted by designated ports only

The correct answer is: Root ports and designated ports transition to the forwarding state

The correct answer highlights the behavior of root ports and designated ports during the spanning tree protocol processes. In a spanning tree topology, once the designated port is elected, it enters the forwarding state, allowing for data traffic to flow through that port. Designated ports are crucial because they connect the segments of the network and are responsible for forwarding frames toward the root bridge. When the spanning tree algorithm is functioning correctly, root ports and designated ports can both transition to the forwarding state, ensuring optimal data transmission throughout the network. This process enables the spanning tree protocol to effectively prevent loops while maintaining a reliable communication path within the local area network (LAN). In contrast, while it may seem that all ports transitioning to a blocking state could facilitate the election process, this does not accurately represent how designated ports operate. The mechanism for breaking ties in designated port election is not simply about root port costs; it involves multiple factors, including the lowest port ID and the lowest bridge ID. The last aspect regarding BPDUs being transmitted only by designated ports addresses the behavior of BPDUs across the network but does not pertain directly to the election process of designated ports during the spanning tree's operation.