NSE7 Advanced VPN and Zero Trust Practice Question
A network administrator is troubleshooting a scenario where remote users can connect via FortiClient VPN but cannot access internal resources. The FortiGate has a valid IPsec VPN configuration. Which THREE checks should the administrator perform to resolve the issue?
⚠ Common exam trap
The trap here is that candidates often focus on tunnel-level settings like MTU or DPD when the real issue is a missing return route or firewall policy, which are common misconfigurations in IPsec VPN deployments.
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
✓
Check if there is a route on the internal network pointing back to the VPN subnet
If the internal network lacks a route back to the VPN subnet (e.g., 10.10.10.0/24), return traffic from internal resources will be dropped or misrouted, preventing remote users from accessing those resources even though the IPsec tunnel is established. This is a classic asymmetric routing issue where the FortiGate sends traffic to the internal network, but the internal router has no path back to the VPN client IPs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Check if there is a route on the internal network pointing back to the VPN subnet
Why this is correct
Without a return route, responses can't reach the VPN clients.
- ✓
Ensure that NAT is disabled on the VPN policy
Why this is correct
NAT on VPN traffic can break connectivity to internal resources.
- ✗
Increase the MTU on the VPN interface
Why it's wrong here
MTU issues cause fragmentation but not complete lack of connectivity.
- ✗
Disable DPD on the VPN phase 1
Why it's wrong here
DPD is for dead peer detection, not access.
- ✓
Verify that the firewall policy allows traffic from the VPN IP pool to the internal network
Why this is correct
If no policy, traffic is dropped.
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 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.