This NSE4 practice question tests your understanding of firewall policies and nat. 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.
A network administrator configures a firewall policy to allow HTTP traffic from the internal network (10.0.0.0/8) to a web server (172.16.1.10). Users on the 10.0.0.0/8 network cannot access the web server, but other internal users can. The administrator checks the policy list and sees the policy is enabled and in the correct position. 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.
The policy is placed below a deny-all policy
Why wrong: The administrator checked policy order and it is correct.
NAT is not configured on the policy
Why wrong: NAT is not required for internal-to-internal traffic.
The firewall does not have a route to the 10.0.0.0/8 network
Without a route, traffic from that network will be dropped.
The policy is disabled
Why wrong: The administrator already verified the policy is enabled.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The firewall does not have a route to the 10.0.0.0/8 network
The most likely cause is that the firewall does not have a route to the 10.0.0.0/8 network. Even though the policy is enabled and correctly positioned, the firewall must have a return route to the source network (10.0.0.0/8) for the web server's response traffic to reach the users. Without this route, the firewall drops the return packets, causing connectivity failure for those specific users.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The policy is placed below a deny-all policy
Why it's wrong here
The administrator checked policy order and it is correct.
NAT is not configured on the policy
Why it's wrong here
NAT is not required for internal-to-internal traffic.
The firewall does not have a route to the 10.0.0.0/8 network
Why this is correct
Without a route, traffic from that network will be dropped.
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 policy is disabled
Why it's wrong here
The administrator already verified the policy is enabled.
Common exam traps
The trap here is that candidates often focus solely on the policy configuration (order, NAT, enablement) and overlook the fundamental requirement that the firewall must have a route to the source network for return traffic to flow correctly.
Detailed technical explanation
In FortiGate firewalls, the routing table must contain a route to the source network (10.0.0.0/8) for the firewall to forward return traffic back to the clients. This is because the firewall performs stateful inspection and must be able to route packets for established sessions. A missing route can be verified using 'get router info routing-table details' or 'diagnose ip route list' commands, and adding a static route (e.g., 'config router static') resolves the issue.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Firewall Policies and NAT — This question tests Firewall Policies and NAT — Read the scenario before looking for a memorised answer..
The correct answer is: The firewall does not have a route to the 10.0.0.0/8 network — The most likely cause is that the firewall does not have a route to the 10.0.0.0/8 network. Even though the policy is enabled and correctly positioned, the firewall must have a return route to the source network (10.0.0.0/8) for the web server's response traffic to reach the users. Without this route, the firewall drops the return packets, causing connectivity failure for those specific users.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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.
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