This ANS-C01 practice question tests your understanding of network design. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company has a VPC with public and private subnets in two Availability Zones. The private subnets host EC2 instances that need to access the internet for software updates. The company must ensure that traffic from the private instances uses a single, predictable public IP address. What is the MOST cost-effective solution?
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 a public subnet in one Availability Zone, and route private subnet traffic to it.
Option C is correct because a NATGateway in a public subnet provides outbound-only internet access for private instances, and it uses a single Elastic IP address, ensuring a predictable public IP. This is the most cost-effective managed solution, as NAT Gateways are highly available within an Availability Zone and require no manual instance management.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Attach an Internet Gateway to the VPC and update the private subnet route table with a default route to the Internet Gateway.
Why it's wrong here
Private subnets cannot route directly to an IGW; they need a NAT device.
✗
Create a Transit Gateway with a VPC attachment and route traffic through a central egress VPC.
Why it's wrong here
Overly complex and costly for this simple requirement.
✓
Deploy a NAT Gateway in a public subnet in one Availability Zone, and route private subnet traffic to it.
Why this is correct
Correct: A single NATGateway provides outbound internet with a predictable IP, and is cost-effective.
Related concept
Read the scenario before looking for a memorised answer.
✗
Launch a NAT instance in a public subnet and configure source/destination check.
Why it's wrong here
NAT instances are less available and require manual management.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may choose Option D (NAT instance) thinking it is cheaper, but they overlook the operational overhead and the fact that a NAT Gateway is fully managed and more cost-effective when factoring in maintenance and availability.
Detailed technical explanation
How to think about this question
A NATGateway uses port address translation (PAT) to map private instance traffic to its Elastic IP, and it automatically handles failover within its Availability Zone. For high availability, you would deploy one NAT Gateway per AZ, but the question specifies a single predictable IP, so one NAT Gateway suffices; traffic from private subnets in other AZs would traverse the NAT Gateway in the same AZ to avoid cross-AZ data transfer costs. The NAT Gateway is managed by AWS, scaling up to 45 Gbps, and supports TCP, UDP, and ICMP, but not protocols like GRE or IPSec.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Deploy a NAT Gateway in a public subnet in one Availability Zone, and route private subnet traffic to it. — Option C is correct because a NAT Gateway in a public subnet provides outbound-only internet access for private instances, and it uses a single Elastic IP address, ensuring a predictable public IP. This is the most cost-effective managed solution, as NAT Gateways are highly available within an Availability Zone and require no manual instance management.
What should I do if I get this ANS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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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.
Question Discussion
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