The answer is that the outgoing interface in the static route is incorrect or down. Even when a static route for the destination network exists in the routing table, the FortiGate will forward packets out the interface specified in that route; if that interface is administratively down, misconfigured, or physically disconnected, the packets leave the FortiGate but never reach the next-hop gateway, and no response returns. On the Fortinet NSE 4 Network Security Professional NSE4 exam, this scenario tests your understanding that a valid route entry does not guarantee reachability—the interface state and correct next-hop association are equally critical. A common trap is assuming that seeing the route in the routing table means traffic will flow, but the sniffer output showing sent packets with no reply is the classic symptom of a dead or wrong interface. Memory tip: “Route exists, but interface is dead—packets leave, no reply ahead.”
NSE4 System and Network Administration Practice Question
This NSE4 practice question tests your understanding of system and network administration. 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.
An administrator runs 'diagnose sniffer packet any "host 10.0.1.100" 4' and sees packets being sent but no response. The FortiGate has a static route for 10.0.1.0/24 via 192.168.1.1. The administrator checks the routing table and sees the route is present. What is the most likely cause of no response?
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
✓
The outgoing interface in the static route is incorrect or down.
Option B is correct because even if the route exists, the outgoing interface might be incorrectly configured. The sniffer shows packets leaving the FortiGate but the destination might not be reachable via that interface. Option A is incorrect because a missing route would show 'no matching route' in debug. Options C and D are less likely given the symptom.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 outgoing interface in the static route is incorrect or down.
Why this is correct
An incorrect interface would cause packets to be sent out the wrong port, not reaching the destination.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The FortiGate has a policy route overriding the static route.
Why it's wrong here
A policy route would be visible in the configuration and could be verified.
✗
The destination host has a firewall blocking ICMP.
Why it's wrong here
This would cause no reply, but the sniffer would still show outgoing packets; the most likely cause is routing.
✗
The static route has a higher administrative distance than a dynamic route.
Why it's wrong here
If present and active, the route should be used regardless of distance.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Trap categories for this question
Command / output trap
This would cause no reply, but the sniffer would still show outgoing packets; the most likely cause is routing.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
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
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related NSE4 NAT questions on configuration and troubleshooting.
System and Network Administration — This question tests System and Network Administration — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The outgoing interface in the static route is incorrect or down. — Option B is correct because even if the route exists, the outgoing interface might be incorrectly configured. The sniffer shows packets leaving the FortiGate but the destination might not be reachable via that interface. Option A is incorrect because a missing route would show 'no matching route' in debug. Options C and D are less likely given the symptom.
What should I do if I get this NSE4 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related NSE4 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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