Cisco
352-001 · Question #112
352-001 Question #112: Real Exam Question with Answer & Explanation
The correct answer is D: PVSTP+. PVSTP+ minimizes unicast flooding during TCN in many-VLAN environments by scoping each topology change to its individual per-VLAN instance and using a gradual timer-based MAC aging process rather than an immediate full flush.
Question
While reviewing an existing network design, you are discussing the characteristics of different STP versions. Which protocol minimizes unicast flooding during TCN in a Layer 2 switched network with many VLANs?
Options
- ASTP
- BMST
- CPVRSTP
- DPVSTP+
Explanation
PVSTP+ minimizes unicast flooding during TCN in many-VLAN environments by scoping each topology change to its individual per-VLAN instance and using a gradual timer-based MAC aging process rather than an immediate full flush.
Common mistakes.
- A. Classic STP (802.1D) maintains one instance for the entire network, so any TCN triggers a global MAC table flush that causes unicast flooding across all VLANs at the same time.
- B. MST groups multiple VLANs into a smaller number of instances, meaning a TCN in one instance simultaneously impacts all VLANs mapped to that instance and can cause flooding across more VLANs than PVSTP+ would.
- C. PVRSTP+ (Rapid PVST+) uses an aggressive TC mechanism that immediately flushes MAC address entries on all non-edge ports upon receiving a TCN, producing a more intense burst of unicast flooding than PVSTP+'s timer-based aging approach.
Concept tested. Per-VLAN STP TCN flooding behavior and comparison
Reference. https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/10556-16.html
Community Discussion
No community discussion yet for this question.