NSE7_SDW Security Profiles Routing And IPsec Practice Question
A FortiGate device is configured with an SD-WAN rule utilizing a SLA rule for latency and packet loss. Security profiles including Deep Packet Inspection (DPI) SSL inspection and an Antivirus profile are applied to the firewall policy allowing this traffic. Users report intermittent connection drops on real-time UDP-based applications. Upon troubleshooting, the administrator notices that packet drops occur only when the SD-WAN rule dynamically steers traffic to a backup IPsec tunnel that has a smaller MTU. What is the most likely root cause and mitigation for this behavior?
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
✓
Path MTU Discovery is failing because ICMP unreachable messages are blocked, and TCP MSS clamping is not adjusting the encapsulated IPsec packet size correctly
IPsec encapsulation adds overhead, and if the Path MTU Discovery (PMTUD) fails due to ICMP fragmentation-needed messages being blocked by security profiles or firewalls along the path, packet drops occur for UDP streams exceeding the actual MTU. Adjusting the TCP MSS or enabling ipsec-phase1-interface fragmentation settings/tcp-mss-enforcement resolves this.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Path MTU Discovery is failing because ICMP unreachable messages are blocked, and TCP MSS clamping is not adjusting the encapsulated IPsec packet size correctly
Why this is correct
Correct. When SD-WAN steers traffic over a tunnel with a smaller MTU, lack of fragmentation or MSS adjustment leads to drops of packets larger than the egress interface MTU.
- ✗
SD-WAN health check probes are overwhelming the IPsec tunnel bandwidth
Why it's wrong here
SD-WAN health check probes consume minimal bandwidth and do not cause application connection drops.
- ✗
The Antivirus proxy buffer is overflowing due to UDP streaming packets
Why it's wrong here
Antivirus inspection handles TCP streams primarily; UDP traffic goes through flow-based or proxy-based inspection differently and does not typically overflow buffers based on MTU mismatch.
- ✗
The SSL inspection profile is attempting to decrypt UDP traffic, causing kernel panic and packet drops
Why it's wrong here
SSL/TLS inspection applies to TCP traffic, not raw UDP streams.
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.
About these practice questions
One of 92 original NSE7_SDW practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official Fortinet exam blueprint
This NSE7_SDW 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_SDW exam.