Spanning Tree Fundamentals: Root Election & Port Roles

Bundle lab · $29.99

Beginner CCNA lab on a redundant two-switch Layer-2 loop with two parallel uplinks. You will enable Rapid-PVST+, set a deterministic root-bridge priority so SW1 becomes the root for VLAN 1, and verify port roles (root/designated/alternate) and loop prevention. Two Alpine hosts in VLAN 1 validate end-to-end connectivity without any routing or SVIs.

Learning objectives

• Enable Rapid-PVST+ globally on Layer-2 switches
• Deterministically elect the STP root by configuring bridge priority
• Interpret RSTP port roles and states (root, designated, alternate/blocking)
• Validate loop prevention with parallel inter-switch links
• Use IOS show commands to confirm STP status per VLAN and interface

Troubleshooting focus

• Wrong switch elected as root due to a lower bridge priority
• Parallel inter-switch links both forwarding due to mode mismatch or disabled STP
• Host-facing ports misconfigured as trunks or missing PortFast/BPDU Guard
• Access VLAN mismatch between host-facing ports across closets