The answer is that the secondary unit will become primary and maintain existing UDP sessions. This occurs because FortiGate HA failover session synchronization is enabled by default for UDP traffic, meaning the session table for UDP is continuously replicated from the primary to the secondary unit. When the primary loses power, the secondary promotes itself and retains those synchronized UDP sessions, allowing seamless continuation of UDP-based communications. On the Fortinet NSE 4 Network Security Professional NSE4 exam, this concept tests your understanding of default session synchronization behavior versus optional TCP synchronization—a common trap is assuming all sessions survive failover. Remember the memory tip: “UDP is Up by Default; TCP needs a Toggle.” This distinction is critical for correctly answering HA failover scenario questions on the exam.
NSE4 High Availability and Diagnostics Practice Question
This NSE4 practice question tests your understanding of high availability and diagnostics. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Exhibit
Refer to the exhibit.
config system ha
set group-name "HA_Group"
set mode a-p
set hbdev "port1" 100
set session-pickup enable
set session-pickup-connectionless enable
set priority 200
end
diagnose sys ha status
HA Health Status: OK
Model: FortiGate-100E
Group: HA_Group
Mode: A-P
Group ID: 0
Debug: 0
Cluster Uptime: 5 days 2 hours 15 mins
Cluster Members:
Member 1 (FGT100E3G17012345)
Role: Primary
Serial: FGT100E3G17012345
Priority: 200
Heartbeat interface: port1 (10.0.0.1)
Heartbeat status: OK
Member 2 (FGT100E3G17012346)
Role: Secondary
Serial: FGT100E3G17012346
Priority: 100
Heartbeat interface: port1 (10.0.0.2)
Heartbeat status: OK
Refer to the exhibit. The HA cluster has been operational for 5 days. The primary unit suddenly loses power. Which of the following will happen?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Refer to the exhibit.
config system ha
set group-name "HA_Group"
set mode a-p
set hbdev "port1" 100
set session-pickup enable
set session-pickup-connectionless enable
set priority 200
end
diagnose sys ha status
HA Health Status: OK
Model: FortiGate-100E
Group: HA_Group
Mode: A-P
Group ID: 0
Debug: 0
Cluster Uptime: 5 days 2 hours 15 mins
Cluster Members:
Member 1 (FGT100E3G17012345)
Role: Primary
Serial: FGT100E3G17012345
Priority: 200
Heartbeat interface: port1 (10.0.0.1)
Heartbeat status: OK
Member 2 (FGT100E3G17012346)
Role: Secondary
Serial: FGT100E3G17012346
Priority: 100
Heartbeat interface: port1 (10.0.0.2)
Heartbeat status: OK
A
The secondary unit will become primary, but all existing sessions will be dropped.
Why wrong: Session pickup is enabled, so sessions should be maintained.
B
The cluster will remain without a primary until the original unit is restored.
Why wrong: The secondary unit will automatically become primary.
C
The secondary unit will become primary and maintain only TCP sessions.
Why wrong: Connectionless session pickup is enabled, so UDP sessions are also maintained.
D
The secondary unit will become primary and maintain existing UDP sessions.
Session pickup and session-pickup-connectionless are enabled, so UDP sessions are preserved.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The secondary unit will become primary and maintain existing UDP sessions.
In a FortiGate HA cluster, session synchronization is enabled by default for UDP sessions but not for TCP sessions (unless specifically configured). When the primary unit fails, the secondary unit takes over as primary and maintains all synchronized sessions, which includes UDP sessions. TCP sessions are not synchronized by default and will be dropped upon failover.
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.
✗
The secondary unit will become primary, but all existing sessions will be dropped.
Why it's wrong here
Session pickup is enabled, so sessions should be maintained.
✗
The cluster will remain without a primary until the original unit is restored.
Why it's wrong here
The secondary unit will automatically become primary.
✗
The secondary unit will become primary and maintain only TCP sessions.
Why it's wrong here
Connectionless session pickup is enabled, so UDP sessions are also maintained.
✓
The secondary unit will become primary and maintain existing UDP sessions.
Why this is correct
Session pickup and session-pickup-connectionless are enabled, so UDP sessions are preserved.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume all sessions are synchronized in an HA cluster, but FortiGate defaults to synchronizing only UDP sessions, not TCP sessions, unless session pickup is explicitly enabled for TCP.
Detailed technical explanation
How to think about this question
FortiGate HA uses session synchronization via the HA heartbeat interface to replicate session tables between cluster members. By default, only UDP sessions are synchronized (configurable via 'set session-sync-dev' and 'set session-pickup' settings). TCP sessions require explicit configuration of session pickup or the use of 'set session-pickup-connectionless' for connectionless protocols. In a real-world scenario, this means that failover for VoIP (UDP) calls is seamless, while HTTP (TCP) connections would need to be re-established.
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.
TExam Day Tips
→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 NSE4 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
High Availability and Diagnostics — This question tests High Availability and Diagnostics — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The secondary unit will become primary and maintain existing UDP sessions. — In a FortiGate HA cluster, session synchronization is enabled by default for UDP sessions but not for TCP sessions (unless specifically configured). When the primary unit fails, the secondary unit takes over as primary and maintains all synchronized sessions, which includes UDP sessions. TCP sessions are not synchronized by default and will be dropped upon failover.
What should I do if I get this NSE4 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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 →
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.
This NSE4 practice question is part of Courseiva's free Fortinet 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 NSE4 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.