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Zorluk: OrtaRapid PVST+ Spanning Tree Protocol Operations and Roles

A Cisco Catalyst switch running Rapid PVST+ has a primary uplink on interface GigabitEthernet0/1 functioning as the Root Port for VLAN 10. Interface GigabitEthernet0/2 connects to a secondary distribution switch and functions as an Alternate Port for VLAN 10 in the Discarding state. If interface GigabitEthernet0/1 suddenly fails, how does Rapid PVST+ handle the state and role transition for interface GigabitEthernet0/2?

  1. Interface GigabitEthernet0/2 immediately transitions to the Root Port role and enters the Forwarding state.Cevap
  2. B
    Interface GigabitEthernet0/2 transitions to the Listening state for 15 seconds and Learning state for 15 seconds before entering Forwarding.
  3. C
    Interface GigabitEthernet0/2 transitions to a Backup Port role and remains in the Discarding state until an explicit topology change notification is acknowledged.
  4. D
    Interface GigabitEthernet0/2 enters the Learning state for 6 seconds before transitioning to the Forwarding state.

Cevap

Interface GigabitEthernet0/2 immediately transitions to the Root Port role and enters the Forwarding state.
Rapid PVST+ (based on IEEE 802.1w) incorporates built-in fast convergence features. An Alternate port is a backup path to the Root Bridge that receives BPDUs from a neighboring switch. When the current Root Port fails, the Alternate port can immediately assume the Root Port role and transition directly into the Forwarding state without waiting for legacy 802.1D forward delay timers.

Adım Adım Çözüm

1
Identify the initial Rapid PVST+ port roles and states for VLAN 10.
GigabitEthernet0/1 is the active Root Port (Forwarding state), and GigabitEthernet0/2 is an Alternate Port (Discarding state).
The Alternate port receives superior BPDUs from another switch, serving as a standby path to the Root Bridge.
2
Analyze the impact of the primary uplink failure on GigabitEthernet0/1.
The switch loses its active path to the Root Bridge via GigabitEthernet0/1.
When the active Root Port fails, the switch must select the next best path to the Root Bridge.
3
Apply Rapid PVST+ (802.1w) fast convergence rules for Alternate ports.
GigabitEthernet0/2 immediately becomes the new Root Port and moves directly to the Forwarding state without passing through Listening or Learning states.
Rapid PVST+ integrates UplinkFast functionality into the protocol design, allowing pre-identified Alternate ports to transition to Forwarding instantly upon Root Port failure.

Anahtar Kavram

Rapid PVST+ Alternate Port Fast Transition Mechanics
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Rapid PVST+ Spanning Tree Protocol Operations and Roles

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