ANS-C01 Network Implementation 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 patches from the internet. The company has a NAT gateway in the public subnet. The route table for the private subnet has a route 0.0.0.0/0 pointing to the NAT gateway. However, the EC2 instance cannot reach the internet. Which additional configuration is needed?
⚠ Common exam trap
The ANS-C01 exam often tests the misconception that a NAT gateway automatically has internet access just because it is in a public subnet, but the public subnet itself must have a route to an internet gateway for the NAT gateway to 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
✓
Ensure the public subnet's route table has a route 0.0.0.0/0 pointing to an internet gateway.
The NAT gateway resides in the public subnet, but it still needs a route to the internet. The public subnet's route table must have a default route (0.0.0.0/0) pointing to an internet gateway (IGW) so that traffic from the NAT gateway can be forwarded to the internet. Without this route, the NAT gateway cannot send traffic beyond the VPC, even though the private subnet's route table correctly points to the NAT gateway.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Assign a public IP address to the EC2 instance.
Why it's wrong here
The instance uses the NAT gateway; a public IP is not needed.
- ✗
Attach a security group to the NAT gateway allowing outbound traffic.
Why it's wrong here
NAT gateways do not have security groups.
- ✗
Add a route to the NAT gateway in the private subnet's route table for destination 0.0.0.0/0.
Why it's wrong here
That route already exists.
- ✓
Ensure the public subnet's route table has a route 0.0.0.0/0 pointing to an internet gateway.
Why this is correct
The NAT gateway needs internet access via the internet gateway.
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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.