NSE7 Advanced VPN and Zero Trust Practice Question
A network administrator is troubleshooting an IPsec VPN tunnel between two FortiGates. The tunnel is up but traffic is not passing. The administrator runs 'diagnose vpn ike gateway list' and sees that the IKE SA has been established. However, 'diagnose vpn tunnel list' shows no IPsec SA entries. What is the most likely cause?
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 phase 2 proposal (encryption, authentication, etc.) does not match between peers
IKE SA established but no IPsec SA indicates that phase 2 parameters are misconfigured or the proposal is not matching.
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 firewall policies are not configured to allow traffic through the tunnel
Why it's wrong here
Traffic would still create an IPsec SA when trigger matches; policies affect traffic flow after SA is established.
- ✓
The phase 2 proposal (encryption, authentication, etc.) does not match between peers
Why this is correct
Phase 2 negotiations fail if the proposal is mismatched, leading to no IPsec SA.
- ✗
The pre-shared key on both sides does not match
Why it's wrong here
Mismatched PSK would prevent IKE phase 1 from completing.
- ✗
The interface MTU is set too low
Why it's wrong here
Low MTU may cause fragmentation issues but would not prevent IPsec SA creation.
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 by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.