Quick Answer
The answer is the pair of commands diagnose vpn ike log-filter and diagnose debug application ike -1. These two commands are the standard starting point for IPsec VPN Phase 1 down troubleshooting commands because they isolate and amplify the Internet Key Exchange (IKE) negotiation process. The log-filter command sets a filter to capture only relevant IKE traffic, while the debug command with the -1 flag enables real-time, verbose output of all IKE messages, allowing you to see exactly where the Phase 1 negotiation fails—whether due to mismatched pre-shared keys, proposal mismatches, or peer unreachability. On the Fortinet NSE 4 Network Security Professional exam, this scenario tests your ability to recall the correct diagnostic tools rather than configuration commands; a common trap is choosing show commands like get vpn ike gateway, which only display static configuration, not live negotiation errors. Remember the mnemonic “Filter First, Debug Deep” to ensure you always apply the log-filter before enabling the debug stream, preventing console overload and zeroing in on the Phase 1 failure.
This NSE4 practice question tests your understanding of authentication and vpn. 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 is troubleshooting an IPsec VPN tunnel that is not establishing. The Phase 1 status shows 'down'. Which TWO commands can help diagnose the issue? (Choose TWO.)
diagnose npu np6 ipsec-sa list
Why wrong: Shows hardware offload SA, not helpful for negotiation issues.
diagnose sys session clear
Why wrong: Clears sessions, not a diagnostic command for IKE.
diagnose debug application ike -1
Enables IKE debugging at the highest level.
diagnose vpn tunnel list
Why wrong: Shows tunnel status but not detailed debug information.
diagnose vpn ike log-filter
Filters IKE logs to specific peers.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
diagnose debug application ike -1
The commands 'diagnose vpn ike log-filter' filters IKE logs, and 'diagnose debug application ike -1' enables detailed IKE debug output. These are standard for troubleshooting IPsec VPN issues.
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.
diagnose npu np6 ipsec-sa list
Why it's wrong here
Shows hardware offload SA, not helpful for negotiation issues.
diagnose sys session clear
Why it's wrong here
Clears sessions, not a diagnostic command for IKE.
diagnose debug application ike -1
Why this is correct
Enables IKE debugging at the highest level.
Related concept
Read the scenario before looking for a memorised answer.
diagnose vpn tunnel list
Why it's wrong here
Shows tunnel status but not detailed debug information.
diagnose vpn ike log-filter
Why this is correct
Filters IKE logs to specific peers.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
Shows hardware offload SA, not helpful for negotiation issues.
Detailed technical explanation
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the NSE4 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which NSE4 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Authentication and VPN — study guide chapter
Learn the concepts, then practise the questions
Authentication and VPN practice questions
Targeted practice on this topic area only
All NSE4 questions
1,000 questions across all exam domains
Fortinet NSE 4 Network Security Professional NSE4 study guide
Full concept coverage aligned to exam objectives
NSE4 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Practise NSE4 questions linked to System and Network Administration.
Practise NSE4 questions linked to Firewall Policies and NAT.
Practise NSE4 questions linked to Authentication and VPN.
Practise NSE4 questions linked to Security Profiles.
Practise NSE4 questions linked to High Availability and Diagnostics.
Practise NSE4 questions linked to NSE4 fundamentals.
Practise NSE4 questions linked to NSE4 scenario.
Practise NSE4 questions linked to NSE4 troubleshooting.
Practice this exam
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Authentication and VPN — This question tests Authentication and VPN — Read the scenario before looking for a memorised answer..
The correct answer is: diagnose debug application ike -1 — The commands 'diagnose vpn ike log-filter' filters IKE logs, and 'diagnose debug application ike -1' enables detailed IKE debug output. These are standard for troubleshooting IPsec VPN issues.
Identify which NSE4 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.