The answer is an implicit deny policy blocking the traffic, as the debug flow message “session denied by forward policy check” directly indicates that no matching forward policy was found for the session. In FortiGate’s stateful inspection, even when a firewall policy appears to allow traffic, the forward policy check evaluates the session against all configured policies in order; if none match, the implicit deny at the end of the policy list drops the session. On the Fortinet NSE 7 Advanced Security NSE7 exam, this scenario tests your understanding of policy evaluation order and the difference between policy configuration and actual traffic matching—a common trap is assuming a policy exists simply because it is listed, when in reality the source, destination, or service may not align. Remember that a successful ping does not guarantee policy match, as ICMP may be permitted by a separate policy or implicit rules. Memory tip: “Forward policy check fails = no policy match = implicit deny.”
NSE7 Troubleshooting and Diagnostics Practice Question
This NSE7 practice question tests your understanding of troubleshooting and diagnostics. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 administrator observes that traffic from an internal user to the internet is being blocked. The firewall policy allows the traffic, and the user can ping external hosts. The administrator runs 'diagnose debug flow' for the user's IP and sees 'session denied by forward policy check'. What is the MOST likely cause?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
There is an implicit deny policy blocking the traffic
Option B is correct. 'session denied by forward policy check' indicates no matching policy, leading to implicit deny.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
There is an implicit deny policy blocking the traffic
Why this is correct
The forward policy check indicates that no explicit policy matches the traffic, so it is denied by the implicit deny.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The antivirus profile has detected a threat and is blocking the session
Why it's wrong here
Antivirus blocking would show a different error, such as 'denied by AV profile'.
✗
The user's traffic is being rate-limited by a traffic shaper
Why it's wrong here
Rate limiting would not deny the session; it would shape it.
✗
The user's source IP is in a local-in policy that denies the traffic
Why it's wrong here
Local-in policies affect traffic destined to the FortiGate itself, not forwarded traffic.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Trap categories for this question
Command / output trap
Antivirus blocking would show a different error, such as 'denied by AV profile'.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related NSE7 ACL questions on filtering logic and placement.
Troubleshooting and Diagnostics — This question tests Troubleshooting and Diagnostics — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: There is an implicit deny policy blocking the traffic — Option B is correct. 'session denied by forward policy check' indicates no matching policy, leading to implicit deny.
What should I do if I get this NSE7 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related NSE7 ACL questions on filtering logic and placement.
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?
Standard ACLs match source addresses.
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