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Question 295 of 1,705

Network Design →hardMultiple ChoiceObjective-mapped

Quick Answer

The correct solution is to deploy a NAT Gateway in a public subnet and add a route in the private subnet route table pointing 0.0.0.0/0 to the NAT Gateway. This works because the NAT Gateway, residing in a public subnet with an Elastic IP, translates private IP addresses to its own public IP for outbound traffic, allowing instances in private subnets to initiate connections to the internet for software updates while blocking any unsolicited inbound traffic. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of managed versus self-managed outbound connectivity—specifically that a NAT Gateway minimizes cost and operational overhead compared to a NAT instance, and that it must be placed in a public subnet with a default route from the private subnet. A common trap is confusing a NAT Gateway with a NAT instance or assuming a private subnet can directly use an Internet Gateway. Memory tip: think “NAT Gateway = managed outbound only, public subnet home, private subnet route.”

ANS-C01 Network Design Practice Question

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 network engineer is designing a VPC with public and private subnets. The private subnets must have outbound internet access for software updates but must not be directly reachable from the internet. The company wants to minimize cost and operational overhead. Which solution meets these requirements?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.

Question 1hardmultiple choice

Review the full subnetting walkthrough →

A
Deploy a NAT Gateway in a public subnet and add a route in the private subnet route table pointing 0.0.0.0/0 to the NAT Gateway.
NAT Gateway allows outbound traffic from private subnets while blocking unsolicited inbound traffic.
B
Use an egress-only internet gateway and route 0.0.0.0/0 to it from the private subnets.
Why wrong: Egress-only internet gateway supports IPv6 only; it cannot route IPv4 traffic.
C
Create a VPC peering connection to a VPC with internet access and route 0.0.0.0/0 through the peering connection.
Why wrong: VPC peering does not provide internet gateway access; the peered VPC would still need a NAT device.
D
Attach an internet gateway to the VPC and add a route in the private subnet route table pointing 0.0.0.0/0 to the internet gateway.
Why wrong: An internet gateway allows inbound connections; private subnets should not have a direct route to an internet gateway.

Full breakdown with real-world context →

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 a public subnet and add a route in the private subnet route table pointing 0.0.0.0/0 to the NAT Gateway.

A NAT Gateway, deployed in a public subnet with an associated Elastic IP, enables instances in private subnets to initiate outbound IPv4 connections to the internet (e.g., for software updates) while preventing unsolicited inbound connections from the internet. Adding a default route (0.0.0.0/0) in the private subnet route table pointing to the NAT Gateway satisfies the requirement for outbound-only internet access with minimal cost and operational overhead, as NAT Gateway is a managed service that scales automatically.

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.

✓
Deploy a NAT Gateway in a public subnet and add a route in the private subnet route table pointing 0.0.0.0/0 to the NAT Gateway.
Why this is correct
NAT Gateway allows outbound traffic from private subnets while blocking unsolicited inbound traffic.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use an egress-only internet gateway and route 0.0.0.0/0 to it from the private subnets.
Why it's wrong here
Egress-only internet gateway supports IPv6 only; it cannot route IPv4 traffic.
✗
Create a VPC peering connection to a VPC with internet access and route 0.0.0.0/0 through the peering connection.
Why it's wrong here
VPC peering does not provide internet gateway access; the peered VPC would still need a NAT device.
✗
Attach an internet gateway to the VPC and add a route in the private subnet route table pointing 0.0.0.0/0 to the internet gateway.
Why it's wrong here
An internet gateway allows inbound connections; private subnets should not have a direct route to an internet gateway.

Common exam traps

Common exam trap: answer the scenario, not the keyword

AWS often tests the misconception that an egress-only internet gateway can be used for IPv4 outbound traffic, or that VPC peering can be used to route internet-bound traffic through another VPC, when in fact both are invalid for this scenario.

Detailed technical explanation

How to think about this question

A NAT Gateway operates at Layer 4, translating private source IPs to its own Elastic IP address using port address translation (PAT), and it maintains stateful connection tracking so that return traffic is correctly forwarded back to the private instance. Unlike a NAT instance, a NAT Gateway is managed by AWS, supports burst rates up to 45 Gbps, and does not require patching or failover configuration, making it the cost-effective and low-overhead choice for production environments. A common subtlety is that NAT Gateways are zone-resilient only within a single Availability Zone, so for high availability you must deploy one per AZ and route traffic accordingly.

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.

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FAQ

Questions learners often ask

What does this ANS-C01 question test?

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 and add a route in the private subnet route table pointing 0.0.0.0/0 to the NAT Gateway. — A NAT Gateway, deployed in a public subnet with an associated Elastic IP, enables instances in private subnets to initiate outbound IPv4 connections to the internet (e.g., for software updates) while preventing unsolicited inbound connections from the internet. Adding a default route (0.0.0.0/0) in the private subnet route table pointing to the NAT Gateway satisfies the requirement for outbound-only internet access with minimal cost and operational overhead, as NAT Gateway is a managed service that scales automatically.

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.

Are there clue words in this question I should notice?

Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Same concept, more angles

1 more ways this is tested on ANS-C01

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. Refer to the exhibit. An EC2 instance in the PrivateSubnet is unable to download patches from the internet. What is the most likely cause?

medium

A.The private subnet is not associated with any route table.
B.The NAT gateway does not support IPv6 traffic.
C.The private subnet does not have MapPublicIpOnLaunch set to true.
✓ D.The PrivateRoute resource references the NAT gateway before it is created.

Why D: Option C is correct. The PrivateRoute uses a NatGatewayId but the NAT gateway is defined after the route in the template, and the route has no DependsOn to ensure the NAT gateway is created first. This can cause a dependency error or the route to reference a non-existent resource. Option A is wrong because the private subnet does not need MapPublicIpOnLaunch. Option B is wrong because NAT gateways do not support IPv6, but the question is about internet access (IPv4). Option D is wrong because the route table is associated with the private subnet.

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Question Discussion

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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.