NSE7 Troubleshooting and Diagnostics Practice Question
You are troubleshooting a VPN phase 2 negotiation failure. The logs show 'no proposal chosen'. What is the MOST likely cause?
⚠ Common exam trap
A common mix-up: candidates confuse phase 1 and phase 2 errors, assuming any 'no proposal chosen' relates to IKE proposals, when in fact the error message is specific to the IPsec SA negotiation in phase 2.
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 settings differ between the peers
The 'no proposal chosen' error in VPN phase 2 indicates that the IPsec peers could not agree on a common set of phase 2 parameters (such as encryption algorithm, authentication algorithm, or PFS group). Since phase 2 negotiation occurs after IKE phase 1 has successfully completed, the issue is specifically with the IPsec SA proposal settings, not with pre-shared keys or IKE version. Therefore, differing phase 2 proposals between the peers are the most likely cause.
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 remote gateway IP is incorrect
Why it's wrong here
This would cause phase 1 failure.
- ✗
The pre-shared key mismatch
Why it's wrong here
PSK mismatch causes phase 1 failure, not phase 2.
- ✗
The IKE version mismatch
Why it's wrong here
IKE version mismatch causes phase 1 failure.
- ✓
The phase 2 proposal settings differ between the peers
Why this is correct
Mismatched algorithms cause 'no proposal chosen'.
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
About these practice questions
Courseiva writes every NSE7 question from scratch — 940 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
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.