Spanning Tree TrainerCCNA

Crown the root bridge, then label every port. Each problem is a new random topology.

Your answer

Inspector

The 4 steps

Root bridge: lowest bridge ID. Compare priority first; only if tied, the lowest MAC.
Root port (one per non-root switch): the port with the lowest total cost to the root. Tied? Lowest neighbor bridge ID, then lowest neighbor port ID.
Designated port (one per link): the end on the switch closest to the root. Tied? Lowest bridge ID wins. Every root bridge port is designated.
Everything else blocks. STP calls it non-designated; RSTP calls it an alternate port.

Port cost reference

Settings

Protocol

Cost method

Show costs on the diagram Varied bridge prioritiesPriority decides the root, not just the MAC Mixed link speeds10 Mbps to 10 Gbps, so costs differ

Extra practice

Parallel linksTwo cables between the same switches Custom port prioritiesPort priority breaks parallel-link ties Legacy hubsShared segments and backup ports

Protocol, cost method and the cost display update the current problem. Other options apply to the next problem.