ANS-C01 Network Implementation Practice Question
A company is designing a multi-tier application in a VPC. The web tier must be accessible from the internet, while the application tier must only be accessible from the web tier. The database tier must be isolated from all other tiers except the application tier. Which TWO network architectures meet these requirements? (Choose TWO.)
⚠ Common exam trap
The ANS-C01 exam often tests the misconception that placing all tiers in private subnets with a NAT gateway can provide inbound internet access, but a NAT gateway only supports outbound-initiated traffic and cannot accept inbound connections from the internet.
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 a public subnet for an Application Load Balancer and private subnets for web, app, and database tiers. Use security groups to restrict traffic between tiers.
It places the Application Load Balancer in a public subnet to receive internet traffic, while the web, app, and database tiers reside in private subnets. Security groups are used to restrict traffic flows: the ALB security group allows inbound HTTP/HTTPS from the internet, the web tier security group allows inbound only from the ALB, the app tier security group allows inbound only from the web tier, and the database tier security group allows inbound only from the app tier. This ensures the application tier is only accessible from the web tier, and the database tier is isolated except from the application tier.
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 single public subnet for all tiers and control access with security groups.
Why it's wrong here
All instances would have public IPs, exposing app and database to the internet.
- ✗
Use private subnets for all tiers and a NAT gateway for internet access from the web tier. Use security groups to control traffic.
Why it's wrong here
No inbound internet access to web tier unless an ALB is in a public subnet.
- ✓
Use a public subnet for an Application Load Balancer and private subnets for web, app, and database tiers. Use security groups to restrict traffic between tiers.
Why this is correct
The ALB in public subnet provides inbound access; private subnets isolate tiers.
- ✗
Use a VPN connection from the on-premises network to access all tiers.
Why it's wrong here
This does not address internet access for the web tier.
- ✓
Use public subnets for the web tier, private subnets for the application tier, and isolated subnets (no route to internet) for the database tier. Use security groups to allow traffic only from the web to app and app to database.
Why this is correct
This provides proper isolation and access control.
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Variation 1. A company is deploying a multi-tier web application in a VPC. The web tier must be accessible from the internet, while the application tier must only be accessible from the web tier. The database tier must only be accessible from the application tier. Which design best meets these requirements?
medium- A.Place all tiers in public subnets and use security groups to control traffic between tiers.
- ✓ B.Place the web tier in public subnets with an internet gateway, and the application and database tiers in private subnets. Use security groups to allow traffic from the web tier to the application tier, and from the application tier to the database tier.
- C.Place all tiers in the same subnet and use network ACLs to restrict traffic between tiers.
- D.Place the web tier in a private subnet and use a NAT gateway for outbound internet access. Place the application and database tiers in public subnets.
Why B: It places the web tier in a public subnet with an Internet Gateway (IGW) for direct internet access, while the application and database tiers reside in private subnets with no direct internet path. Security groups act as stateful virtual firewalls at the instance level, allowing you to specify inbound rules that permit traffic only from the web tier security group to the application tier, and from the application tier security group to the database tier. This layered approach enforces the principle of least privilege and meets the access requirements without exposing the internal tiers to the internet.
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.