Rapid Spanning Tree (IEEE 802.1w): On Cisco switches, which global configuration command enables the 802.1w RSTP behavior?

Introduction / Context:
Rapid Spanning Tree Protocol (RSTP), standardized as IEEE 802.1w, accelerates convergence compared to the original 802.1D STP. Cisco implements RSTP per-VLAN with the rapid-pvst mode (Rapid-PVST+).

Given Data / Assumptions:

• Command must be entered in global configuration (config) mode.
• We want Cisco’s RSTP implementation across VLANs.
• Exact keyword syntax matters.

Concept / Approach:
On IOS, spanning tree mode choices typically include pvst, rapid-pvst, and mst. There is no literal mode 802.1w command. Therefore, the correct configuration uses the Rapid-PVST keyword in config mode.

Step-by-Step Solution:

Verification / Alternative check:
Use show spanning-tree and show spanning-tree summary to verify RSTP timers/roles (alternate/backup ports appear only in RSTP).

Why Other Options Are Wrong:

• EXEC mode variants (with # prompt) do not set persistent configuration.
• mode 802.1w is not valid syntax.
• mstp-rapid is not a Cisco keyword.

Common Pitfalls:
Confusing RSTP (rapid-pvst) with MST (spanning-tree mode mst); mixing modes across a Layer 2 domain causing PVST simulation issues.

Final Answer:
Switch(config)# spanning-tree mode rapid-pvst