ANS-C01 Network Design Practice Question
A startup is launching a new web application on AWS and needs to design a highly available and secure network architecture. The application will run on EC2 instances in an Auto Scaling group across two Availability Zones in a single region. The application must be accessible from the internet over HTTPS. The company expects variable traffic and wants to reduce costs where possible. They also need to protect against common web exploits like SQL injection and cross-site scripting. Which combination of AWS services should be used for the network design?
⚠ Common exam trap
Many exam-takers confuse the placement of load balancers and instances, mistakenly thinking that placing the ALB in private subnets is acceptable or that a VPC endpoint can replace a NAT gateway for general outbound internet access.
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
✓
Use an Application Load Balancer (ALB) in public subnets. Enable AWS WAF on the ALB. Place EC2 instances in private subnets with a NAT gateway for outbound traffic.
An Application Load Balancer (ALB) in public subnets can terminate HTTPS and distribute traffic to EC2 instances in private subnets, which enhances security by removing direct internet access from the instances. Enabling AWS WAF on the ALB protects against common web exploits like SQL injection and cross-site scripting. A NAT gateway in public subnets provides outbound internet access for instances in private subnets, which is cost-effective for variable traffic as it scales automatically and incurs charges only when used.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use an Application Load Balancer (ALB) in private subnets. Enable AWS WAF on the ALB. Place EC2 instances in public subnets with a VPC endpoint for outbound traffic.
Why it's wrong here
ALB in private subnets cannot be accessed from the internet. Also, instances in public subnets with public IPs are less secure.
- ✓
Use an Application Load Balancer (ALB) in public subnets. Enable AWS WAF on the ALB. Place EC2 instances in private subnets with a NAT gateway for outbound traffic.
Why this is correct
ALB provides HTTP/HTTPS termination, integrates with WAF for web exploit protection, and supports private subnet instances.
- ✗
Use an Application Load Balancer (ALB) in public subnets. Use a VPC endpoint for outbound traffic. Place EC2 instances in public subnets with Elastic IPs.
Why it's wrong here
Instances in public subnets with Elastic IPs are directly exposed to the internet, increasing attack surface. VPC endpoints are not for general outbound internet traffic.
- ✗
Use a Network Load Balancer (NLB) in public subnets. Enable AWS Shield Advanced for DDoS protection. Place EC2 instances in private subnets with a NAT gateway for outbound traffic.
Why it's wrong here
NLB operates at layer 4 and does not support WAF integration for application-layer protection like SQL injection.
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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.