ANS-C01 Network Design Practice Question
A company is designing a network for a three-tier application that must be PCI DSS compliant. The web tier must be accessible from the internet, the application tier must only be accessible from the web tier, and the database tier must only be accessible from the application tier. All tiers are in the same VPC. What is the MOST secure way to implement this?
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
✓
Place web tier in public subnets, application and database tiers in private subnets. Use security groups to allow only necessary traffic between tiers.
The most secure because it places the web tier in public subnets (for internet access) and the application and database tiers in private subnets (no direct internet access). Security groups are used to allow only the necessary traffic between tiers: from web to app on specific ports, and from app to db on specific ports. Security groups are stateful, which simplifies rule management and reduces attack surface. Option A is wrong because a VPN is unnecessary for intra-VPC traffic and adds complexity without improving security. Option B is wrong because placing all tiers in the same private subnet does not provide network isolation between tiers; security groups alone cannot prevent all lateral movement. Option D is wrong because placing all tiers in public subnets exposes the application and database tiers to the internet, and network ACLs are stateless, requiring symmetric rules and increasing management overhead.
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 a VPN between the web and application tiers and between application and database tiers.
Why it's wrong here
VPN adds unnecessary complexity for intra-VPC communication.
- ✗
Place all tiers in the same private subnet and use security groups for isolation.
Why it's wrong here
Same subnet does not provide network isolation; security groups alone are not enough for best practice.
- ✓
Place web tier in public subnets, application and database tiers in private subnets. Use security groups to allow only necessary traffic between tiers.
Why this is correct
Security groups provide stateful filtering and are best practice for tier isolation.
- ✗
Place all tiers in public subnets and use network ACLs to restrict traffic.
Why it's wrong here
Public subnets expose resources; network ACLs are stateless and complex.
Visual reference
Go deeper
Related to this question
About these practice questions
This ANS-C01 question is part of Courseiva's 1,621-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
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.