Jeremy's IT Lab - CCNA Course: Rapid Spanning Tree

Introduction

• This video focuses on rapid spanning tree, specifically Cisco's Rapid Per-VLAN Spanning Tree Plus (Rapid PVST+).
• Classic spanning tree can take up to 50 seconds to converge; rapid spanning tree improves convergence to a few seconds.
• Rapid spanning tree is now the default and covered in the CCNA exam.

Spanning Tree Protocol Versions

Industry Standards

• 802.1D: Classic Spanning Tree Protocol, all VLANs share one STP instance, no load balancing.
• 802.1w: Rapid Spanning Tree Protocol, faster convergence, still one shared STP instance.
• 802.1s: Multiple Spanning Tree Protocol, allows grouping VLANs into different instances for load balancing.

Cisco Proprietary Versions

• PVST+: Cisco's upgrade to 802.1D, each VLAN has its own STP instance for load balancing.
• Rapid PVST+: Cisco's upgrade to 802.1w, maintains rapid convergence and supports per-VLAN STP instances.

Rapid Spanning Tree Protocol (RSTP)

Key Features

• Not timer-based; uses a handshake mechanism for faster port state transitions.
• Port roles include root, designated, alternate, and backup.
• Alternate Port: Discovers superior BPDU from another switch, can quickly switch to forwarding if the root port fails.
• Backup Port: Receives superior BPDU from the same switch, used in rare hub situations.

Port States

• Discarding: Combines classic STP's blocking and disabled states, no traffic forwarding.
• Learning and Forwarding: Retained from classic STP, forwarding sends traffic and learns MAC addresses.

Port Costs

• Updated for faster port speeds in RSTP (e.g., 20 for 1 Tbps).

STP Optional Features in RSTP

• Integrated features like UplinkFast, BackboneFast, and PortFast (edge port functionality).

Differences Between Classic STP and RSTP

• All switches send their own BPDUs in RSTP, not just the root.
• Faster BPDU aging in RSTP, considers a neighbor lost after 3 missed BPDUs (6 seconds).

RSTP Link Types

• Edge: Connected to end hosts, enables immediate forwarding (PortFast function).
• Point-to-Point: Direct switch-to-switch connections, full-duplex.
• Shared: Connected to hubs, operates in half-duplex.

CLI Commands

• Configure Rapid PVST+ using: spanning-tree mode rapid-pvst
• Verify using: show spanning-tree

Conclusion

• Rapid PVST+ offers rapid convergence, per-VLAN load balancing, and integrates multiple classic STP optional features.
• Recommended for small to medium networks; MSTP for large networks.

Quiz & Practice

• Questions on identifying port roles, link types, and understanding integrated features.
• Practice exams recommended: Boson Software’s ExSim for CCNA preparation.

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• Supplementary Materials: Flashcards and packet tracer labs available in next video.
• Acknowledgments: Shoutout to JCNP-level channel members for their support.