ANS-C01 Network Design Practice Question
A company has a VPC with public and private subnets in three Availability Zones. They want to provide outbound internet access to instances in private subnets while preventing inbound traffic from the internet. Which solution meets these requirements with the least operational overhead?
⚠ Common exam trap
Watch out — candidates often confuse a NAT Gateway with a NAT instance, assuming both offer similar operational overhead, or mistakenly think that an Internet Gateway can be used directly in private subnets, ignoring that it would allow inbound traffic 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
✓
Create a NAT Gateway in a public subnet and add a default route in the private subnet route table pointing to the NAT Gateway.
A NAT Gateway is a fully managed AWS service that provides outbound internet access for instances in private subnets while blocking unsolicited inbound connections. By placing the NAT Gateway in a public subnet and adding a default route (0.0.0.0/0) in the private subnet route table pointing to the NAT Gateway, traffic from private instances is source NATed to the NAT Gateway's Elastic IP, ensuring inbound traffic from the internet cannot reach the private instances. This solution offers the least operational overhead as AWS handles scaling, patching, and availability, unlike a self-managed NAT instance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Deploy a NAT instance in a public subnet and configure the private subnet route table to point to it.
Why it's wrong here
NAT instances require management overhead for scaling and patching.
- ✗
Attach an Internet Gateway to the VPC and add a default route to it in the private subnet route table.
Why it's wrong here
This would allow inbound traffic from the internet to private instances.
- ✓
Create a NAT Gateway in a public subnet and add a default route in the private subnet route table pointing to the NAT Gateway.
Why this is correct
NAT Gateway is a managed service, reduces operational overhead.
- ✗
Create a VPC Gateway Endpoint for Amazon S3 and route outbound traffic through it.
Why it's wrong here
VPC endpoint only provides access to supported AWS services, not general internet.
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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.