The wrong switch is the spanning-tree root
Three switches in a triangle, and STP elected the wrong root, so traffic takes a bad path. Make the intended switch the root, loop-free.
Scenario
Three switches (sw1, sw2, sw3) are cabled in a triangle for redundancy. STP is doing its job (the topology is loop-free), but it elected the wrong root: a low priority left behind from an old design pins the root on sw3, and that puts the root in the wrong place, so traffic between access switches takes a suboptimal path. You want sw1 to be the root.
Topology
- sw1, sw2, sw3 in a triangle (each pair connected). One VLAN.
Your job
Make sw1 the spanning-tree root for the VLAN, and confirm the triangle stays loop-free (one port in a blocking state).
What "done" looks like
show spanning-tree on sw1 reports it is the root, and one link in the triangle is blocking.
Teaches: STP root election, why you set the root deliberately (priority) instead of letting MAC addresses decide, and reading which port blocks to break the loop.
Tooling
Arista cEOS. Validate syntax on first deploy.
What gets checked
Your solution is verified against each of these:
- sw1 is the spanning-tree root bridge for the VLAN
- STP has converged with a blocking port, so the triangle is loop-free
Solve it in your browser
No setup, no install. Write your solution in the editor and hit Check. The in-house engine renders and grades it instantly, then issues your proof the moment every check passes.
Solve in browser →Prefer your own lab?
- Build the fix locally. New to the tooling? See setting up your lab.
- Push your topology file, device configs, and any playbooks to a public repo (GitHub or GitLab).
- Submit the repo link. We review it by hand, confirm it works, and issue your proof page.