NSE7 Troubleshooting and Diagnostics Practice Question
A FortiGate is configured with a site-to-site IPsec VPN to a remote office. Users at the remote office report that they cannot access resources at the main office. The administrator checks the VPN status and sees that the tunnel is up. Which two actions should the administrator take to troubleshoot the issue? (Choose two.)
⚠ Common exam trap
The trap here is assuming that a tunnel being up means all traffic will pass, but phase2 selector mismatches or policy issues can still block traffic.
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
✓
Run 'diagnose debug flow' with filters for the source and destination IPs.
Since the IPsec tunnel is up, the issue is likely with data traffic not being properly routed or encrypted. Using diagnose debug flow with filters will trace the packet path and reveal where packets are dropped. Checking phase2 selectors ensures that the traffic matches the encryption domain; mismatched selectors are a common cause of connectivity failures even when the tunnel is established.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Run 'diagnose debug application ike -1' to check for IKE errors.
Why it's wrong here
This command is used to debug IKE negotiations, which are part of establishing the VPN tunnel. Since the tunnel is already up, IKE errors are unlikely to be the cause of the connectivity issue. The problem is likely with data traffic, so debugging IKE would not help and may produce unnecessary output.
- ✗
Run 'diagnose vpn tunnel list' to view the tunnel status.
Why it's wrong here
This command shows the status of VPN tunnels, which the administrator already knows is up. It does not provide information about why data traffic is not passing. While useful for verifying tunnel status, it does not help diagnose the current issue, which is likely related to traffic flow or selectors.
- ✗
Restart the IPsec VPN tunnel by clearing the IKE gateway.
Why it's wrong here
Restarting the tunnel might temporarily resolve issues but does not help in troubleshooting the root cause. Since the tunnel is already up, the problem is likely with traffic handling, not the tunnel itself. Restarting could disrupt other users and is not a diagnostic step.
- ✓
Run 'diagnose debug flow' with filters for the source and destination IPs.
Why this is correct
The debug flow command traces packet processing and can show if traffic is being dropped by a policy, routing issue, or other problem. Since the tunnel is up, the issue is likely with data traffic not being encrypted or decrypted correctly. Using debug flow with appropriate filters will help identify where the packets are being dropped.
- ✓
Check the IPsec phase2 selectors to ensure they match the interesting traffic.
Why this is correct
Phase2 selectors define which traffic is encrypted and sent through the tunnel. If the selectors do not match the traffic, packets will not be sent through the VPN. This is a common cause of connectivity issues even when the tunnel is up. Verifying the selectors ensures that the intended traffic is being routed into the tunnel.
Visual reference
Quick reference
VPN Protocol Comparison
| Protocol | Port | Encryption | Authentication | Use Case |
|---|---|---|---|---|
| IKEv2 / IPsec | UDP 500 / 4500 | AES-256 | Certificates / PSK | Site-to-site & remote access |
| SSL / TLS VPN | TCP 443 | TLS 1.3 | Certificates / MFA | Clientless remote access |
| L2TP / IPsec | UDP 1701 | AES (IPsec) | PSK / Certificates | Legacy remote access |
| WireGuard | UDP 51820 | ChaCha20 | Public keys | Modern high-performance VPN |
| PPTP | TCP 1723 | MPPE (weak) | MS-CHAPv2 | Legacy — avoid in production |
PPTP is considered insecure. IKEv2/IPsec and SSL VPN are the current recommended options.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Fortinet exam blueprint
This NSE7 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 NSE7 exam.