STP vs RSTP Explained — How One Cable Can Crash a Network
One Ethernet cable can create a Layer 2 loop, trigger a broadcast storm, cause MAC address flapping, and bring an entire network to its knees.
In this beginner-friendly networking lab, I demonstrate how Spanning Tree Protocol protects a Cisco switch from a physical loop and explain the difference between traditional STP and Rapid Spanning Tree Protocol.
You’ll learn:
• What Spanning Tree Protocol actually does
• How a Layer 2 switching loop forms
• Why Ethernet frames can continue circulating
• How broadcast storms affect switch performance
• What MAC address flapping looks like
• How BPDUs detect redundant paths
• The difference between STP and RSTP
• Blocking, listening, learning and forwarding
• Discarding, learning and forwarding
• How an IP phone pass-through port can accidentally create a loop
This demonstration was performed on an isolated lab switch. Never disable Spanning Tree or intentionally create a switching loop on a production network.
This is Part 1 of The Panic Room Spanning Tree series.
Part 2 will cover PVST+, Rapid PVST+, multiple switches and per-VLAN Spanning Tree behavior.
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Welcome to The Panic Room — where we create switching loops in the lab so you don’t create them in production.
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