- A
A switch that detects a topology change sends a TCN BPDU toward the root bridge.
Correct because the TCN (Topology Change Notification) is sent to inform the root bridge of a change.
- B
The root bridge sets the Topology Change (TC) flag in its BPDUs after receiving a TCN.
Correct because the root bridge propagates the TC flag to all switches, triggering MAC table flushing.
- C
When the TC flag is set, switches reduce the MAC address aging timer to the forward delay time.
Correct because this flushes stale MAC entries quickly, allowing the network to relearn paths.
- D
The Max Age timer is used to flush MAC address entries during a topology change.
Why wrong: Incorrect because Max Age is used to age out BPDU information, not MAC addresses.
- E
The forward delay timer determines how long a switch waits before transitioning from listening to learning state.
Why wrong: 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.
Quick Answer
The answer is that when the TC flag is set, switches reduce the MAC address aging timer to the forward delay time. This is correct because in the STP topology change TCN BPDU process, a switch detecting a link change sends a TCN BPDU toward the root bridge, which then broadcasts BPDUs with the TC flag set. All downstream switches respond by shortening their MAC aging timer from the default 300 seconds to the forward delay time (typically 15 seconds), flushing stale entries and forcing rapid relearning of the new topology. On the ENCOR 350-401 exam, this concept tests your understanding of convergence mechanics, often appearing in multiple-choice questions that ask which three statements are true. A common trap is confusing the TC flag’s effect on MAC aging with the Max Age timer, which actually ages BPDUs, not MAC addresses. Remember: TC flag = flush MACs fast; Max Age = kill old BPDUs.
CCNP Spanning Tree Protocol Practice Question
This 350-401 practice question tests your understanding of spanning tree protocol. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
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.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
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.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 350-401 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
- →
Spanning Tree Protocol — study guide chapter
Learn the concepts, then practise the questions
- →
Spanning Tree Protocol practice questions
Targeted practice on this topic area only
- →
All 350-401 questions
2,015 questions across all exam domains
- →
ENCOR 350-401 study guide
Full concept coverage aligned to exam objectives
- →
350-401 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 350-401 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Architecture practice questions
Practise 350-401 questions linked to Architecture.
Enterprise Network Design practice questions
Practise 350-401 questions linked to Enterprise Network Design.
SD-Access Architecture practice questions
Practise 350-401 questions linked to SD-Access Architecture.
SD-WAN Architecture practice questions
Practise 350-401 questions linked to SD-WAN Architecture.
QoS Architecture practice questions
Practise 350-401 questions linked to QoS Architecture.
Virtualization practice questions
Practise 350-401 questions linked to Virtualization.
Network Function Virtualization practice questions
Practise 350-401 questions linked to Network Function Virtualization.
Virtual Machines and Hypervisors practice questions
Practise 350-401 questions linked to Virtual Machines and Hypervisors.
VRF and Path Isolation practice questions
Practise 350-401 questions linked to VRF and Path Isolation.
Infrastructure practice questions
Practise 350-401 questions linked to Infrastructure.
OSPF practice questions
Practise 350-401 questions linked to OSPF.
BGP practice questions
Practise 350-401 questions linked to BGP.
Practice this exam
Start a free 350-401 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this 350-401 question test?
Spanning Tree Protocol — This question tests Spanning Tree Protocol — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this 350-401 question wrong?
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 18, 2026
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.