- A
The user's traffic is not traversing the FortiGate
Why wrong: Debug flow shows the traffic matching the policy, so it is traversing.
- B
The log queue is overflowing and logs are being dropped
If the log rate exceeds the ability to write to disk, logs can be dropped. The admin should check 'diagnose log device status' and 'diagnose log test'.
- C
The logging filter is set to only log 'emergency' severity
Why wrong: If logging is enabled for all sessions, the filter is not the issue, but the severity for traffic logs is typically 'information'.
- D
The log disk is full and cannot accept new logs
Why wrong: A full disk would cause logs to be dropped, but the admin would see disk full alerts. However, the more precise technical reason for missing logs when logging is enabled is often log buffer overflow or rate limiting. Both A and D are plausible, but A is more specific to the symptom of no logs appearing despite configuration. However, the correct answer is A because disk full would cause a different behavior (old logs might be overwritten or logging stops). Actually, FortiGate may still log to memory buffer even if disk is full, but logs may be lost when buffer is full. The question is ambiguous, but typically the issue is log overflow. I'll choose A.
Quick Answer
The answer is that the log queue is overflowing and logs are being dropped. Even when a firewall policy has logging enabled for all sessions, the FortiGate must process and write each log entry to its configured storage, such as local disk or a syslog server. If the rate of traffic generating logs exceeds the system’s ability to write them, the log buffer fills up and new logs are simply discarded, which explains why the debug flow shows the traffic matching the policy but no entries appear in the traffic log. On the Fortinet NSE 4 exam, this scenario tests your understanding of log resource management and the difference between policy configuration and system capacity—a common trap is assuming that enabling logging guarantees every session is recorded. Remember the memory tip: “Logging enabled does not mean logging delivered; if the queue is full, the log is null.”
NSE4 High Availability and Diagnostics Practice Question
This NSE4 practice question tests your understanding of high availability and diagnostics. 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 admin is troubleshooting why a user's traffic is not being logged. The firewall policy has logging enabled at 'All Sessions'. The admin checks the traffic log and sees no entries for that user. The admin runs 'diagnose debug flow' and sees the traffic is matching the policy. What could be the issue?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The log queue is overflowing and logs are being dropped
If the traffic is matching the policy but not appearing in logs, the most common reason is that the log buffer is full or logs are being dropped due to high rate. Alternatively, the log device (e.g., disk) might be full or the log queue is overflowing. Another possibility is that the log severity filter is too restrictive, but by default traffic logs are logged at 'information' severity. The scenario says logging is enabled, so the issue is likely log buffer overflow or disk full. Option D addresses log disk space or buffer overflow.
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 user's traffic is not traversing the FortiGate
Why it's wrong here
Debug flow shows the traffic matching the policy, so it is traversing.
- ✓
The log queue is overflowing and logs are being dropped
Why this is correct
If the log rate exceeds the ability to write to disk, logs can be dropped. The admin should check 'diagnose log device status' and 'diagnose log test'.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
The logging filter is set to only log 'emergency' severity
Why it's wrong here
If logging is enabled for all sessions, the filter is not the issue, but the severity for traffic logs is typically 'information'.
- ✗
The log disk is full and cannot accept new logs
Why it's wrong here
A full disk would cause logs to be dropped, but the admin would see disk full alerts. However, the more precise technical reason for missing logs when logging is enabled is often log buffer overflow or rate limiting. Both A and D are plausible, but A is more specific to the symptom of no logs appearing despite configuration. However, the correct answer is A because disk full would cause a different behavior (old logs might be overwritten or logging stops). Actually, FortiGate may still log to memory buffer even if disk is full, but logs may be lost when buffer is full. The question is ambiguous, but typically the issue is log overflow. I'll choose A.
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
Debug flow shows the traffic matching the policy, so it is traversing.
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.
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FAQ
Questions learners often ask
What does this NSE4 question test?
High Availability and Diagnostics — This question tests High Availability and Diagnostics — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The log queue is overflowing and logs are being dropped — If the traffic is matching the policy but not appearing in logs, the most common reason is that the log buffer is full or logs are being dropped due to high rate. Alternatively, the log device (e.g., disk) might be full or the log queue is overflowing. Another possibility is that the log severity filter is too restrictive, but by default traffic logs are logged at 'information' severity. The scenario says logging is enabled, so the issue is likely log buffer overflow or disk full. Option D addresses log disk space or buffer overflow.
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.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 21, 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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