The answer is that session synchronization is not enabled between HA members. When a FortiGate cluster with VDOMs fails over, the new primary unit inherits the synchronized configuration but lacks the runtime session table from the original primary. Without session synchronization, the new primary treats returning packets as new connections, which are dropped if they do not match the initial handshake state of a firewall policy—a common issue in HA failover VDOM session synchronization scenarios. On the Fortinet NSE 7 Advanced Security NSE7 exam, this question tests your understanding that configuration sync and session sync are separate processes; a frequent trap is assuming that HA configuration replication includes active session states. Remember the memory tip: “Config sync copies the blueprint, session sync copies the active construction.”
NSE7 Enterprise Firewall and VDOMs Practice Question
This NSE7 practice question tests your understanding of enterprise firewall and vdoms. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
A FortiGate in an HA cluster with VDOMs enabled experiences a failover. After the failover, traffic that was passing before is now being dropped. The configuration is synchronized between the primary and secondary units. What is the most likely reason?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Session synchronization is not enabled between HA members
The most likely reason is that session synchronization is not enabled between HA members. When a failover occurs, the new primary FortiGate does not have the existing session table entries from the original primary, so it treats incoming packets as new connections and may drop them if they do not match a firewall policy's initial handshake state. Even though the configuration is synchronized, session information is not shared unless session synchronization is explicitly configured, causing traffic to be dropped after 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 new primary has a different VDOM configuration
Why it's wrong here
VDOM config is synchronized; should be identical.
✗
The firewall policies are not synchronized
Why it's wrong here
Policies are synchronized; the statement says config is synchronized.
✓
Session synchronization is not enabled between HA members
Why this is correct
Without session sync, the new primary lacks session information for existing connections, causing drops until clients retransmit.
Clue confirmation
The clue words "most likely", "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
VDOM link interfaces are down on the new primary
Why it's wrong here
If VDOM links were part of HA, they would fail over; unlikely cause.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume synchronized configuration includes session state, but FortiGate HA separates configuration sync from session sync, and session synchronization must be enabled as a separate setting under the HA configuration.
Detailed technical explanation
How to think about this question
Session synchronization in FortiGate HA uses the session sync daemon (sessionsync) to replicate TCP/UDP session tables over the HA heartbeat link. Without it, the new primary must re-establish all sessions from scratch, which can cause drops for stateful protocols like TCP if the three-way handshake was completed on the old primary. In real-world scenarios, this is critical for VoIP or long-lived database connections where session loss leads to application timeouts.
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 NSE7 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.
Enterprise Firewall and VDOMs — This question tests Enterprise Firewall and VDOMs — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Session synchronization is not enabled between HA members — The most likely reason is that session synchronization is not enabled between HA members. When a failover occurs, the new primary FortiGate does not have the existing session table entries from the original primary, so it treats incoming packets as new connections and may drop them if they do not match a firewall policy's initial handshake state. Even though the configuration is synchronized, session information is not shared unless session synchronization is explicitly configured, causing traffic to be dropped after failover.
What should I do if I get this NSE7 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: "most likely", "primary". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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