NSE7 Advanced VPN and Zero Trust Practice Question
A FortiGate administrator is troubleshooting an IPsec VPN that uses IKEv2 with certificate authentication. The VPN fails to establish. The administrator runs 'diagnose vpn ike gateway list' and sees the gateway state is 'IKE_INIT'. Which three possible causes should the administrator investigate? (Choose three.)
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 certificate of the remote peer is not trusted by the local FortiGate
The IKE_INIT state indicates phase 1 has not completed. Possible causes include the remote peer's certificate not being trusted (A), phase 1 proposal mismatch (C), and the remote peer's certificate having expired (E). Note that with IKEv2 certificate authentication, a pre-shared key (B) is not used, and phase 2 proxy ID mismatch (D) would not cause phase 1 failure.
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 certificate of the remote peer is not trusted by the local FortiGate
Why this is correct
Certificate validation failure would cause IKE to stay in INIT.
- ✗
The pre-shared key is incorrect
Why it's wrong here
IKEv2 with certificate authentication does not use pre-shared key.
- ✓
The phase 1 proposal (encryption, hash, DH group) does not match
Why this is correct
Proposal mismatch prevents IKE from moving past INIT.
- ✗
The phase 2 proxy ID is incorrect
Why it's wrong here
Phase 2 parameters are negotiated after IKE_AUTH; they would not cause IKE_INIT state.
- ✓
The remote peer's certificate has expired
Why this is correct
Expired certificate would fail validation.
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.
Go deeper
Related to this question
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This NSE7 question is part of Courseiva's 940-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more way this is tested on NSE7
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A FortiGate administrator is troubleshooting a VPN tunnel that uses IKEv2 with certificate authentication. The tunnel fails to establish, and the IKE debug shows 'no acceptable proposal' for the initial exchange. Which TWO configuration mismatches could cause this error? (Choose two.)
medium- ✓ A.Mismatched encryption algorithms between the two peers
- B.Mismatched phase2 encryption algorithms
- C.Mismatched IKE version (IKEv1 vs IKEv2)
- D.Incorrect local certificate configuration on one peer
- ✓ E.Mismatched authentication methods (pre-shared key vs certificate)
Why A: 'No acceptable proposal' in IKEv2 phase1 indicates a mismatch in proposal parameters. Encryption algorithm mismatch (A) and authentication method mismatch (E: pre-shared key vs certificate) can both cause this error. Phase2 mismatches (B) occur later, not during initial exchange.
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.