ANS-C01 Network Management and Operations Practice Question
A company has deployed a Network Load Balancer (NLB) in front of a fleet of EC2 instances in a VPC. The NLB is configured with a TCP listener on port 443. Clients are experiencing timeouts. The target group health checks are passing. What is the most likely cause?
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 security group for the EC2 instances does not allow traffic from the NLB.
Security groups must allow traffic from the NLB's private IP addresses. Option A is incorrect because cross-zone load balancing affects distribution, not timeouts. Option B is incorrect because health checks passing means targets are healthy. Option D is incorrect because deletion protection prevents accidental deletion, not timeouts.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Cross-zone load balancing is disabled.
Why it's wrong here
Cross-zone balancing affects traffic distribution, not connectivity.
- ✗
Deletion protection is enabled on the NLB.
Why it's wrong here
Deletion protection does not affect traffic.
- ✓
The security group for the EC2 instances does not allow traffic from the NLB.
Why this is correct
NLB uses its own IP addresses; security group must allow them.
- ✗
The target group is using an incorrect health check path.
Why it's wrong here
Health checks are passing, so the path is correct.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This ANS-C01 practice question is part of Courseiva's free Amazon Web Services 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 ANS-C01 exam.