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Difficulty: MediumRapid PVST+ Spanning Tree Protocol Operations and Roles

A network administrator is reviewing the layer 2 topology operational characteristics on a Cisco Catalyst switch block running Rapid PVST+. Which two statements accurately describe the port roles and operational state transitions of Rapid PVST+?

  1. An Alternate port receives BPDUs from neighboring switches and provides an alternate backup path toward the Root Bridge.Answer
  2. Rapid PVST+ streamlines protocol port states to Discarding, Learning, and Forwarding, eliminating the separate Disabled, Blocking, and Listening states used in 802.1D.Answer
  3. C
    A network engineer can set the global bridge priority to any arbitrary value such as 4100 to force root selection.
  4. D
    Enabling Spanning Tree PortFast on an inter-switch trunk port ensures immediate forwarding transition without risk of layer 2 loops.

Answer

The two correct statements are that an Alternate port receives BPDUs from neighboring switches to act as a backup path to the Root Bridge, and that Rapid PVST+ simplifies port states into Discarding, Learning, and Forwarding.
Rapid PVST+ simplifies 802.1D port states into Discarding, Learning, and Forwarding while introducing the Alternate port role as a pre-calculated backup path to the Root Bridge that receives BPDUs from alternate neighboring switches.

Step-by-Step Solution

1
Analyze Rapid PVST+ port roles
Identify that an Alternate port offers a direct backup path to the Root Bridge via another switch, while a Backup port offers a redundant path on a shared segment from the same switch.
Rapid PVST+ explicitly defines Alternate and Backup port roles to facilitate immediate proposal/agreement convergence.
2
Analyze Rapid PVST+ port states
Confirm that Rapid PVST+ merges Disabled, Blocking, and Listening into the Discarding state.
RSTP (802.1w) optimized port state efficiency by maintaining only three operational states: Discarding, Learning, and Forwarding.
3
Evaluate invalid bridge priority and PortFast claims
Reject arbitrary bridge priorities (must use 4096 increments) and trunk PortFast configurations.
System ID extension enforces 4096 step increments, and PortFast on trunks removes loop protection.

Key Concept

Rapid PVST+ Port Roles and Port State Operations
Estimated Time:1m 30s
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Topics

Rapid PVST+ Spanning Tree Protocol Operations and Roles

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