ANS-C01 Network Implementation Practice Question
A company is designing a network for a multi-tier application that includes a web tier, application tier, and database tier. The web tier must be accessible from the internet, while the application and database tiers should have no direct internet access. All tiers are in the same VPC. Which configuration meets these requirements?
⚠ Common exam trap
The ANS-C01 exam often tests the misconception that security groups or NACLs alone can fully isolate tiers from the internet when placed in public subnets, ignoring that a public subnet’s route to an Internet Gateway inherently allows inbound traffic unless explicitly blocked by a firewall or stateful inspection.
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 with Internet Gateway, app and DB tiers in private subnets with a NAT Gateway for outbound traffic
It places the web tier in a public subnet with an Internet Gateway (IGW) for direct inbound internet traffic, while the application and database tiers reside in private subnets with no direct internet path. A NAT Gateway in a public subnet provides outbound-only internet access for the private tiers (e.g., for software updates) without allowing inbound connections, satisfying the requirement that only the web tier be internet-accessible.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Place all tiers in public subnets and use security group rules to restrict access to app and DB tiers
Why it's wrong here
Public subnets have direct route to internet, so tiers are exposed.
- ✓
Place web tier in public subnets with Internet Gateway, app and DB tiers in private subnets with a NAT Gateway for outbound traffic
Why this is correct
This design provides internet access to web tier while isolating app and DB tiers.
- ✗
Place web tier in a public subnet and app and DB tiers in the same public subnet but with restrictive Network ACLs
Why it's wrong here
Network ACLs can limit inbound but cannot prevent outbound internet access if route exists.
- ✗
Place all tiers in private subnets and attach an Internet Gateway to the private subnets for the web tier
Why it's wrong here
Internet Gateway requires a public subnet route table.
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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.