NSE7 Advanced Networking and SD-WAN Practice Question
During an SD-WAN health check, an administrator observes that a performance SLA for wan1 shows 'Status: dead' even though the interface is up and can ping the SLA server. The SLA configuration uses a TCP echo probe to 8.8.8.8 port 443. What is the most likely cause?
⚠ Common exam trap
Many exam-takers assume a successful ICMP ping to the SLA server means all probes should work, overlooking that TCP echo probes require a specific service (TCP echo on port 7 or a custom port that echoes data) and that port 443 on 8.8.8.8 does not provide that service.
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 probe protocol is TCP echo, but the server at 8.8.8.8 does not support TCP echo on port 443.
The TCP echo probe sends a TCP SYN to the specified port and expects a SYN-ACK to confirm connectivity. 8.8.8.8 (Google DNS) does not run a TCP echo service on port 443; it serves HTTPS. The server will respond with a TCP RST or simply ignore the probe, causing the SLA to fail and show 'dead' even though the interface is up and ICMP ping works.
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 SLA server is blocking ICMP echo requests.
Why it's wrong here
The probe uses TCP, not ICMP.
- ✗
The performance SLA is configured with the wrong threshold.
Why it's wrong here
Thresholds affect status but not the probe failure itself.
- ✗
The firewall policy allowing the probe traffic is missing.
Why it's wrong here
If the interface is up and ping works, the policy likely allows traffic; the issue is the probe type.
- ✓
The probe protocol is TCP echo, but the server at 8.8.8.8 does not support TCP echo on port 443.
Why this is correct
TCP echo uses port 7 by default; using a different port will not elicit a proper echo response unless the server is configured for it.
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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.