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IntermediatePublished 2026-07-02

STP Lab 7: Rapid-PVST+ Migration on Triangle Loop

Bundle lab

Migrate a three-switch triangle from legacy PVST to Rapid-PVST+ without changing the existing root or blocked port. SW1 remains the deterministic root for VLAN 70 (priority 4096). Verify protocol mode, link types (point-to-point vs edge), and end-to-end host reachability, then observe the faster reconvergence behavior of Rapid-PVST+.

Track
Est. time
45 minutes
Difficulty
Intermediate
Topics

Learning objectives

  • Enable Rapid-PVST+ globally on all switches in a looped L2 topology.
  • Maintain deterministic root control for VLAN 70 using bridge priority (SW1 at 4096).
  • Verify protocol mode change with show spanning-tree summary.
  • Confirm trunk ports are detected as point-to-point and access ports as edge with show spanning-tree vlan 70 detail.
  • Validate connectivity between hosts across a spanning-tree blocked/alternate path scenario and observe faster convergence.

Troubleshooting focus

  • One switch left in PVST while others run Rapid-PVST+ leads to mixed behavior and slower convergence.
  • Trunk allow-list drift can silently prune VLAN 70 across part of the triangle.
  • Access port missing PortFast/BPDU Guard risks long convergence or topology corruption if a host bridges BPDUs.
  • Incorrect root priority on a non-root switch can steal root and change port roles unexpectedly.

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How this lab is graded
  • Build it your way. Where a lab lets you choose a value — a VLAN name, an interface description — grading checks that you configured it, not which name you picked. Names that another line has to reference, like an ACL applied with access-class, are stated in the guide and do have to match.
  • Addresses, modes and protocol keywords are exact. An IP address, a subnet mask, switchport mode trunk, an encapsulation — these carry the meaning of the lab, so they are graded as written in the guide.
  • Grading reads your saved configuration. Export the lab from CML after you have configured it, and make sure anything you set is in the running-config — a change that only exists in a terminal session never reaches the grader.
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