NSE7 Advanced VPN and Zero Trust Practice Question
A FortiGate administrator sees the following syslog message repeatedly: 'IPsec phase 2 failed to establish SA with peer due to proposal mismatch.' The administrator has already verified that the phase 2 parameters (encryption, authentication, PFS, and lifetime) match on both sides. What else should the administrator check?
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 local and remote subnets defined in the phase 2 selector
Phase 2 negotiation can also fail due to mismatched traffic selectors (local and remote subnets).
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 local and remote subnets defined in the phase 2 selector
Why this is correct
Mismatched traffic selectors will cause phase 2 negotiation to fail.
- ✗
The phase 1 proposal settings
Why it's wrong here
Phase 1 is already established; phase 2 failure is separate.
- ✗
The DPD configuration
Why it's wrong here
DPD affects keepalives, not proposal matching.
- ✗
The pre-shared key
Why it's wrong here
PSK is used only in phase 1.
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 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.