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Zorluk: Çok zorRapid PVST+ Spanning Tree Protocol Operations and Roles

Place the tie-breaking criteria evaluated by a non-root switch running Rapid PVST+ in the correct sequence (from first evaluated to last evaluated) when selecting its Root Port.

  1. 1Lowest cumulative Root Path Cost contained in received BPDUs
  2. 2Lowest Designated (Sender) Bridge ID
  3. 3Lowest Designated (Sender) Port ID
  4. 4Lowest Local Port ID on the receiving switch

Cevap

The correct sequence for Rapid PVST+ Root Port selection tie-breaking is: 1) Lowest cumulative Root Path Cost, 2) Lowest Designated (Sender) Bridge ID, 3) Lowest Designated (Sender) Port ID, and 4) Lowest Local Port ID on the receiving switch.
Rapid PVST+ evaluates Root Port selection strictly in sequence: cumulative path cost first, followed by upstream sender Bridge ID, upstream sender Port ID, and finally the local receiving Port ID as a last resort.

Adım Adım Çözüm

1
Identify the primary criterion for Root Port selection in Spanning Tree operations.
Path cost evaluation is performed first.
The switch determines the shortest administrative distance to the Root Bridge by adding the local port cost to the root path cost reported in the incoming BPDU.
2
Evaluate the first tie-breaker if path costs are equal.
Designated (Sender) Bridge ID is evaluated.
When equal-cost paths originate from different neighboring switches, the switch prefers the neighbor with the lowest Bridge ID (Priority + System ID Extension + MAC Address).
3
Evaluate the second tie-breaker if receiving BPDUs from the same neighbor across parallel links.
Designated (Sender) Port ID is evaluated.
When parallel links connect to the same upstream switch, the neighbor Bridge ID is identical, so the sender's Port ID (Port Priority + Port Number) breaks the tie.
4
Evaluate the final tie-breaker if BPDUs arrive on different local interfaces from the exact same remote port.
Local Port ID is evaluated.
If all sender parameters are identical, the local receiving switch uses its own lowest Port ID (Port Priority + Port Number) as the definitive tie-breaker.

Anahtar Kavram

Rapid PVST+ Root Port Selection Algorithm
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Rapid PVST+ Spanning Tree Protocol Operations and Roles

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