The answer is that the policy is missing the 'set inspection-mode proxy' command. This is correct because FortiGate requires proxy-based inspection mode to perform SSL/TLS interception; flow-based inspection cannot decrypt or re-encrypt HTTPS traffic, so without this command the policy defaults to flow-based mode, causing SSL inspection to fail even if an ssl-ssh-profile is set to deep-inspection. On the Fortinet NSE 4 Network Security Professional NSE4 exam, this tests your understanding of the critical distinction between proxy and flow inspection modes—a common trap is assuming that applying a deep-inspection profile alone is sufficient, when in fact the policy must explicitly enable proxy mode for SSL decryption to work. A helpful memory tip: think of "proxy" as the only mode that can "pause and peek" inside encrypted traffic, while flow mode merely "passes it through" without decryption.
NSE4 Security Profiles Practice Question
This NSE4 practice question tests your understanding of security profiles. 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 firewall policy
edit 1
set name "SSL-Inspection"
set srcintf "wan1"
set dstintf "internal"
set srcaddr "all"
set dstaddr "all"
set action accept
set schedule "always"
set service "ALL"
set utm-status enable
set ssl-ssh-profile "deep-inspection"
set profile-protocol-options "default"
set av-profile "default"
set webfilter-profile "default"
next
end
Refer to the exhibit. An administrator is troubleshooting why SSL inspection is not working for web traffic. The policy shown is the only policy matching the traffic. What is the most likely reason SSL inspection is failing?
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.
Refer to the exhibit.
config firewall policy
edit 1
set name "SSL-Inspection"
set srcintf "wan1"
set dstintf "internal"
set srcaddr "all"
set dstaddr "all"
set action accept
set schedule "always"
set service "ALL"
set utm-status enable
set ssl-ssh-profile "deep-inspection"
set profile-protocol-options "default"
set av-profile "default"
set webfilter-profile "default"
next
end
A
The policy is missing the 'set inspection-mode proxy' command.
Deep inspection requires proxy-based inspection mode.
B
The ssl-ssh-profile is set to 'deep-inspection' but the policy is using flow-based inspection.
Why wrong: This is essentially the same as B, but B is more precise.
C
The source interface is 'wan1' but the traffic is coming from 'internal'.
Why wrong: The exhibit shows the policy matches traffic from wan1 to internal, which is correct for inbound inspection.
D
The policy has 'set action deny' instead of 'set action accept'.
Why wrong: The action is accept, so traffic is allowed.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The policy is missing the 'set inspection-mode proxy' command.
Option A is correct because the policy is missing the 'set inspection-mode proxy' command. FortiGate requires proxy-based inspection mode to perform SSL/TLS interception; flow-based inspection cannot decrypt or re-encrypt HTTPS traffic. Without this command, the policy defaults to flow-based mode, causing SSL inspection to fail even if the ssl-ssh-profile is set to deep-inspection.
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 policy is missing the 'set inspection-mode proxy' command.
Why this is correct
Deep inspection requires proxy-based inspection mode.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The ssl-ssh-profile is set to 'deep-inspection' but the policy is using flow-based inspection.
Why it's wrong here
This is essentially the same as B, but B is more precise.
✗
The source interface is 'wan1' but the traffic is coming from 'internal'.
Why it's wrong here
The exhibit shows the policy matches traffic from wan1 to internal, which is correct for inbound inspection.
✗
The policy has 'set action deny' instead of 'set action accept'.
Why it's wrong here
The action is accept, so traffic is allowed.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume setting the ssl-ssh-profile to 'deep-inspection' alone is sufficient, overlooking the mandatory 'set inspection-mode proxy' command required for SSL decryption to function.
Trap categories for this question
Command / output trap
The exhibit shows the policy matches traffic from wan1 to internal, which is correct for inbound inspection.
Detailed technical explanation
How to think about this question
FortiGate supports two inspection modes: proxy-based and flow-based. Proxy-based mode terminates the client SSL connection, decrypts the traffic, applies security profiles (including deep inspection), then re-encrypts and forwards to the server. Flow-based mode uses a single-pass architecture that cannot perform SSL termination; it only inspects packet headers and cannot decrypt HTTPS payloads. The 'set inspection-mode proxy' command is required under the firewall policy to enable SSL interception, even when the ssl-ssh-profile is configured for deep inspection.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
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.
Security Profiles — This question tests Security Profiles — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The policy is missing the 'set inspection-mode proxy' command. — Option A is correct because the policy is missing the 'set inspection-mode proxy' command. FortiGate requires proxy-based inspection mode to perform SSL/TLS interception; flow-based inspection cannot decrypt or re-encrypt HTTPS traffic. Without this command, the policy defaults to flow-based mode, causing SSL inspection to fail even if the ssl-ssh-profile is set to deep-inspection.
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: "most likely". 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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Question Discussion
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