The correct architecture uses an internet-facing Application Load Balancer in public subnets paired with an internal Application Load Balancer in private subnets that targets the web servers. This two-tier design ensures the web servers remain isolated from direct internet access while still receiving traffic through the internal ALB’s private IP addresses, satisfying the security requirement. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of internal application load balancer architecture and how to layer load balancers to enforce network segmentation. A common trap is placing web servers in public subnets behind a single internet-facing ALB, which still exposes the servers to potential direct access if security group rules are misconfigured. The key insight is that an internal ALB never exposes its endpoints to the internet, so traffic must flow from the internet-facing ALB to the internal ALB, then to the servers. Memory tip: think “front door, inner door” — the internet-facing ALB is the front door, and the internal ALB is the inner door that keeps the servers hidden.
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is deploying a web application in a VPC with public and private subnets. The web servers in public subnets must be protected from direct internet access, but they need to receive traffic from an Application Load Balancer (ALB). Which architecture should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Internet-facing ALB in public subnets, and internal ALB in private subnets pointing to web servers
Option C is correct because it uses an internet-facing ALB in public subnets to receive traffic from the internet, then forwards it to an internal ALB in private subnets, which distributes traffic to web servers in private subnets. This ensures the web servers are not directly accessible from the internet, meeting the security requirement while still allowing traffic from the ALB. The internal ALB uses private IP addresses, keeping the web servers isolated from direct internet access.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Internet-facing ALB in public subnets with web servers also in public subnets
Why it's wrong here
Web servers would be directly accessible from the internet, violating security.
✗
Internal Network Load Balancer in private subnets with web servers
Why it's wrong here
NLB does not provide HTTP/HTTPS termination needed for web applications.
✓
Internet-facing ALB in public subnets, and internal ALB in private subnets pointing to web servers
Why this is correct
This allows traffic to flow through the internet-facing ALB to the internal ALB, keeping web servers private.
Related concept
Read the scenario before looking for a memorised answer.
✗
Amazon CloudFront with origin pointing to web servers in public subnets
Why it's wrong here
Web servers are still publicly accessible.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume an internet-facing ALB alone can protect servers in public subnets, but the key requirement is that servers must not be directly accessible from the internet, which necessitates placing them in private subnets and using an internal ALB for internal routing.
Detailed technical explanation
How to think about this question
Under the hood, the internet-facing ALB in public subnets terminates the client connection and initiates a new connection to the internal ALB using private IP addresses, ensuring no direct path from the internet to the web servers. The internal ALB operates at layer 7 (HTTP/HTTPS) and can perform health checks and routing without exposing the servers to the internet. In a real-world scenario, this architecture is common for multi-tier applications where the web tier must be isolated, and it also allows for centralized SSL termination at the internet-facing ALB.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Internet-facing ALB in public subnets, and internal ALB in private subnets pointing to web servers — Option C is correct because it uses an internet-facing ALB in public subnets to receive traffic from the internet, then forwards it to an internal ALB in private subnets, which distributes traffic to web servers in private subnets. This ensures the web servers are not directly accessible from the internet, meeting the security requirement while still allowing traffic from the ALB. The internal ALB uses private IP addresses, keeping the web servers isolated from direct internet access.
What should I do if I get this ANS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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