Spanning Tree Protocol
Switching
Overview
STP prevents L2 loops by electing a root bridge and selecting forwarding paths while blocking redundant ones. Lowest bridge ID wins root election; path cost guides root-port selection with tie-breakers. RSTP improves convergence. STP is not part of the legacy topology forwarding engine; this is a separate decision exercise.
Protocol stages
- 1Bridge IDs
- 2Root election
- 3Path-cost comparison
- 4Port roles
- 5Loop-free tree
Interactive exercise
Knowledge check
Bridge IDs are 4096:AA, 32768:BB and 32768:CC. Which becomes root?
Educational model — not real hardware, traffic or official certification.