NSE7 Advanced VPN and Zero Trust Practice Question
An administrator is troubleshooting an IPsec VPN tunnel that fails to establish. The configuration uses certificates for authentication. The admin sees the following log message: 'Certificate validation failed: unable to get local issuer certificate.' What is the most likely cause?
⚠ Common exam trap
The trap is confusing this error with an expired certificate or CRL issue. The specific phrase 'unable to get local issuer certificate' points directly to a missing CA certificate.
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 that signed the peer's certificate is not imported on the FortiGate
The error 'unable to get local issuer certificate' indicates that the FortiGate cannot find the CA certificate that signed the peer's certificate in its local store. Without the CA certificate, the FortiGate cannot validate the peer's certificate chain. Importing the correct CA certificate resolves the issue.
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 peer's certificate has expired
Why it's wrong here
An expired peer certificate yields an expiry-specific validation error, whereas 'unable to get local issuer certificate' means the issuing CA certificate cannot be located to build the chain. Expiry is the cause when the log names validity dates.
- ✓
The CA certificate that signed the peer's certificate is not imported on the FortiGate
Why this is correct
The error means the FortiGate cannot build a chain to a trusted root for the peer's certificate. Importing the issuing CA certificate into the local store lets the FortiGate validate the peer's certificate chain, resolving the 'unable to get local issuer certificate' failure.
- ✗
The certificate revocation list (CRL) is not configured
Why it's wrong here
A missing CRL produces a revocation-status error, not the 'unable to get local issuer certificate' message, which indicates the intermediate CA certificate is absent from the local store. CRL configuration matters when the gateway must confirm a peer certificate has not been revoked.
- ✗
The local certificate does not match the peer's expected CN
Why it's wrong here
A CN mismatch fails identity verification after the chain validates, producing a peer-ID or DN mismatch error rather than an issuer lookup failure. CN checking is relevant when the gateway must confirm the peer's identity matches the configured remote gateway.
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.