NSE7 Advanced VPN and Zero Trust Practice Question
A FortiGate VPN administrator is configuring IKEv2 with certificate-based authentication using a PKI. The administrator has imported the CA certificate and the local certificate onto the FortiGate. When initiating the VPN, the tunnel fails to establish. The CLI log shows 'IKEv2 authentication failed' and 'certificate validation failure'. What is the most likely missing configuration?
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 CA certificate is not configured for peer certificate validation
For certificate-based authentication, the FortiGate must be configured to verify the peer's certificate against the trusted CA. Option D is correct because the peer's certificate must be validated, and if the CA certificate is not properly referenced in the phase1 configuration (e.g., 'set certificate-peers' or 'set enforcesecrets'), validation fails.
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 IKEv2 proposal includes an incompatible encryption algorithm
Why it's wrong here
Proposal mismatch would cause 'no proposal chosen', not certificate validation failure.
- ✗
The local certificate is not associated with the phase1 interface
Why it's wrong here
The local certificate must be set, but the error indicates peer certificate validation failure, not local certificate issue.
- ✗
The remote peer's certificate is not signed by the imported CA
Why it's wrong here
If the remote certificate is not signed by the CA, validation would fail, but the admin likely imported the correct CA; the issue might be that the CA is not used for validation.
- ✓
The CA certificate is not configured for peer certificate validation
Why this is correct
The phase1 must include a reference to the CA certificate (via 'set ca-cert' or 'set certificate-peer') to validate the peer's certificate. Without this, the FortiGate does not know which CA to trust.
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.