ANS-C01 Network Design Practice Question
A company has a VPC with a public subnet and a private subnet. An EC2 instance in the private subnet needs to download updates from the internet. The company wants to minimize costs and avoid exposing the instance to inbound internet traffic. Which solution should the engineer choose?
⚠ Common exam trap
The ANS-C01 exam often tests the misconception that a NAT instance can be placed in a private subnet, but in reality, it must reside in a public subnet with a route to an Internet Gateway to perform its function.
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
✓
Deploy a NAT Gateway in the public subnet and add a route in the private subnet route table pointing to the NAT Gateway.
A NAT Gateway in the public subnet allows instances in the private subnet to initiate outbound connections to the internet (e.g., for updates) while remaining unreachable from inbound internet traffic. The private subnet's route table must have a default route (0.0.0.0/0) pointing to the NAT Gateway, which then uses the Internet Gateway for outbound traffic. This is the most cost-effective and fully managed solution compared to a NAT instance, as it avoids per-instance management and scales automatically.
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 the private subnet and route traffic through it.
Why it's wrong here
NAT instance is less reliable and higher maintenance than NAT Gateway.
- ✓
Deploy a NAT Gateway in the public subnet and add a route in the private subnet route table pointing to the NAT Gateway.
Why this is correct
NAT Gateway provides outbound internet access, cost-effective and managed.
- ✗
Configure a forward proxy on the EC2 instance itself.
Why it's wrong here
Proxy on instance does not help other instances and adds complexity.
- ✗
Attach an internet gateway to the VPC and add a route to the internet gateway in the private subnet's route table.
Why it's wrong here
Private subnet instances do not have public IPs; internet gateway alone won't work.
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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.