Root Bridge (STP/RSTP)
The root bridge is the reference switch in STP; all path decisions are made relative to it.
Updated: 2026-03-05
Definition
STP elects a root bridge based on bridge ID (priority + MAC).
Switches calculate the shortest path to the root and block redundant links to prevent loops.
Key points
- Lowest bridge ID wins (priority first)
- Root placement affects traffic paths
- Set root intentionally for predictable topology
Common mistakes
- Leaving root election to chance (random MAC wins).
- Accidentally making an access switch the root.
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