← All simulators
Network Access Simulator
Spanning Tree — Watch the Election & the Blocked Port
Three switches in a triangle have a physical loop. Spanning Tree elects one root, then blocks exactly one port to break the loop. Change the bridge priorities to move the root, then fail a link and watch the blocked port spring to Forwarding as the tree reconverges.
R Root port · D Designated — Forwarding A Alternate — Blocking
🎛️ Run the election
Make root (sets priority 24576)
Fail a link (pull the cable)
📜 What spanning tree did
- All switches are default priority 32768, so the lowest MAC (SW1) is root. Change a priority or fail a link to see the tree recompute.
Practice — Spanning Tree
Score: 0 / 0
A question each round — instant feedback, CCNA exam format.
Question
—
Drill this into reflex
Claim my free session →Stop guessing which port blocks
1:1 mentorship with real switching scenarios, lab reviews, and US interview prep. Free first session. No card on file.