NSE7 Advanced VPN and Zero Trust Practice Question
A FortiGate administrator is configuring an IPsec VPN with IKEv2 between two sites. The administrator wants to ensure that the VPN tunnel uses perfect forward secrecy (PFS) and that the phase 2 selectors are restricted to specific subnets. Which two configuration elements are required to meet these goals? (Choose two.)
⚠ Common exam trap
Watch out — candidates often confuse phase 1 DH group with phase 2 PFS; PFS specifically requires a DH group in phase 2 proposals.
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
✓
Configure local and remote subnets in the phase 2 selectors.
To achieve PFS, a DH group must be configured in the phase 2 proposals, which triggers a new key exchange for each phase 2 SA. To restrict the tunnel to specific subnets, the local and remote subnets must be defined in the phase 2 selectors. Together, these two elements ensure that the VPN meets both the PFS and subnet restriction requirements. Other options do not directly contribute to these goals.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable auto-negotiation in phase 2.
Why it's wrong here
Auto-negotiation in phase 2 allows the FortiGate to dynamically create phase 2 selectors based on traffic, which is useful in dial-up or hub-and-spoke scenarios. However, it does not enforce specific subnets; instead, it can create broader selectors. This would not meet the goal of restricting phase 2 selectors to specific subnets. Auto-negotiation is not required for PFS either, as PFS is controlled by the DH group in phase 2 proposals. Therefore, this option is incorrect.
- ✓
Configure local and remote subnets in the phase 2 selectors.
Why this is correct
Phase 2 selectors define the traffic that is allowed through the tunnel. To restrict the VPN to specific subnets, the administrator must configure the local and remote subnets in the phase 2 selectors. This ensures that only traffic between those subnets is encrypted and sent through the tunnel. Without this, the tunnel might use 0.0.0.0/0, allowing all traffic. Thus, this is required to meet the goal of restricted selectors.
- ✗
Set the phase 1 proposal to use a DH group.
Why it's wrong here
A DH group in phase 1 is used for the initial key exchange and is required for IKEv2, but it does not provide PFS for phase 2. PFS requires a separate DH exchange in phase 2. While phase 1 DH is necessary for the tunnel to establish, it does not fulfill the PFS requirement. The administrator must configure a DH group in phase 2 proposals, not just phase 1. Hence, this is not a correct choice for the stated goals.
- ✓
Configure a DH group in phase 2 proposals.
Why this is correct
PFS is achieved by specifying a Diffie-Hellman group in the phase 2 proposals. Without a DH group in phase 2, the keys are derived from the phase 1 key material, and PFS is not provided. The administrator must select a DH group (e.g., group 14) in the phase 2 proposal to ensure that a new key exchange occurs for each phase 2 SA, providing PFS. This is a required element for the stated goal.
- ✗
Enable replay detection in phase 2.
Why it's wrong here
Replay detection protects against replay attacks by tracking sequence numbers, but it does not provide PFS or restrict phase 2 selectors. It is a security feature but unrelated to the goals. Enabling it would not help achieve PFS or specific subnet restriction. Therefore, it is not a required configuration element for this scenario.
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.