ANS-C01 Network Implementation Practice Question
A company has a VPC with a public subnet and a private subnet. They have a NAT Gateway in the public subnet. They also have an EC2 instance in the private subnet that needs to access the internet. The route table for the private subnet has a default route (0.0.0.0/0) pointing to the NAT Gateway. The security group for the EC2 instance allows outbound HTTPS traffic. The network ACL for the private subnet allows inbound and outbound ephemeral ports. However, the EC2 instance cannot reach the internet. The network engineer checks the NAT Gateway and sees that it has an Elastic IP attached. The engineer also checks the route table for the public subnet and finds no route to the internet. What should the engineer do to fix the issue?
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
✓
Add a route in the public subnet route table to 0.0.0.0/0 via the internet gateway.
The NAT Gateway resides in the public subnet, and for the NAT Gateway to forward traffic to the internet, the public subnet's route table must have a default route (0.0.0.0/0) pointing to an internet gateway. Without that route, the NAT Gateway cannot send traffic to the internet, even though the private subnet's route points to the NAT Gateway. Options A, C, and D are incorrect: A is unnecessary because a NAT Gateway in the private subnet would not have direct internet access; C would bypass the NAT Gateway and require a route to the internet gateway directly from the private subnet, which is not the standard design; D is wrong because adding another Elastic IP does not solve the missing route issue.
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 second NAT Gateway in the private subnet.
Why it's wrong here
NAT gateways must be in public subnets.
- ✓
Add a route in the public subnet route table to 0.0.0.0/0 via the internet gateway.
Why this is correct
This allows the NAT gateway to reach the internet.
- ✗
Add a route in the private subnet route table to 0.0.0.0/0 via the internet gateway.
Why it's wrong here
The private subnet should route through the NAT gateway, not directly to IGW.
- ✗
Attach a second Elastic IP to the NAT Gateway.
Why it's wrong here
NAT gateway only needs one EIP; multiple EIPs are not supported.
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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.