ANS-C01 Network Design Practice Question
A company is designing a network for a three-tier web application in a single VPC. The web tier must be accessible from the internet, but the application and database tiers must not have direct internet access. The application servers need to make outbound calls to a third-party API. Which architecture meets these requirements?
⚠ Common exam trap
Many candidates confuse an internet gateway with a NAT gateway, assuming an internet gateway can provide outbound-only access from private subnets, but an internet gateway requires public IPs and allows bidirectional traffic, while a NAT gateway specifically enables outbound-only traffic from private subnets.
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
✓
Web servers in public subnets with an Application Load Balancer, application servers in private subnets with a NAT gateway, and database servers in private subnets.
It places web servers in public subnets with an Application Load Balancer for inbound internet traffic, while application and database servers reside in private subnets without direct internet access. A NAT gateway in a public subnet enables the application servers to initiate outbound connections to a third-party API, with return traffic automatically routed back, meeting the requirement for outbound-only internet access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Web servers in public subnets, application and database servers in private subnets with an internet gateway for outbound traffic.
Why it's wrong here
Private subnets need a NAT device for outbound internet access, not an internet gateway.
- ✗
All servers in public subnets with security groups restricting access.
Why it's wrong here
Public subnets expose application and database servers unnecessarily.
- ✓
Web servers in public subnets with an Application Load Balancer, application servers in private subnets with a NAT gateway, and database servers in private subnets.
Why this is correct
This follows best practices for a three-tier architecture.
- ✗
All servers in private subnets and a VPN connection to the internet.
Why it's wrong here
A VPN to the internet is not a standard solution for outbound traffic.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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