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350-401 Practice Question: Which three statements about STP topology changes…
Which three statements about STP topology changes and convergence are true? (Choose three.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A switch that detects a topology change sends a TCN BPDU toward the root bridge.
When a topology change occurs in 802.1D STP, the switch that detects the change sends a TCN BPDU toward the root bridge. The root bridge then sets the TC flag in its BPDUs, causing all switches to shorten their MAC address aging timers to flush stale entries. This process ensures rapid convergence of the forwarding database. The Max Age timer is used to age out BPDU information, not to flush MAC addresses. The forward delay timer is used during listening and learning states, not directly for MAC aging.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
A switch that detects a topology change sends a TCN BPDU toward the root bridge.
Why this is correct
Correct because the TCN (Topology Change Notification) is sent to inform the root bridge of a change.
- ✓
The root bridge sets the Topology Change (TC) flag in its BPDUs after receiving a TCN.
Why this is correct
Correct because the root bridge propagates the TC flag to all switches, triggering MAC table flushing.
- ✓
When the TC flag is set, switches reduce the MAC address aging timer to the forward delay time.
Why this is correct
Correct because this flushes stale MAC entries quickly, allowing the network to relearn paths.
- ✗
The Max Age timer is used to flush MAC address entries during a topology change.
Why it's wrong here
Incorrect because Max Age is used to age out BPDU information, not MAC addresses.
- ✗
The forward delay timer determines how long a switch waits before transitioning from listening to learning state.
Why it's wrong here
Incorrect because the forward delay timer applies to both listening and learning states, but it is not directly related to MAC aging during topology changes.
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.