200-301 Question 212
Single answerA network administrator is troubleshooting a topology where Rapid PVST+ is enabled. They notice that some ports on a switch are transitioning to the forwarding state much faster than others. What mechanism in Rapid PVST+ is responsible for this faster convergence?
- A
PortFast
- B
UplinkFast
- C
Bridge Protocol Data Units (BPDUs)
- D
Proposal and Agreement process
Show answer and explanation
Correct answer: D
Explanation
Rapid PVST+ enhances standard Spanning Tree Protocol by introducing mechanisms to achieve faster convergence. One critical feature is the Proposal and Agreement process, which allows switches to quickly transition ports to the forwarding state while maintaining a loop-free topology. This process is key to Rapid PVST+'s efficiency during topology changes, especially compared to the traditional STP convergence process.
- A. Incorrect.
PortFast is used to immediately transition edge ports (connected to end devices) to the forwarding state, bypassing the usual STP states. However, it is not responsible for faster convergence during topology changes involving non-edge ports.
- B. Incorrect.
UplinkFast is used to quickly transition a blocked port to the forwarding state on an access switch when the primary link fails. While it aids in faster convergence, it is not the mechanism used during Rapid PVST+ topology changes.
- C. Incorrect.
BPDUs are used to exchange Spanning Tree information between switches. While they are essential to the operation of Rapid PVST+, they do not directly account for faster convergence.
- D. Correct.
The Proposal and Agreement process is a mechanism introduced in Rapid PVST+ to achieve faster convergence by immediately transitioning designated and root ports to the forwarding state after ensuring a loop-free topology.