The answer is that the route table for the public subnet lacks a route to an Internet Gateway. This is the most likely cause because a NAT Gateway must reside in a public subnet that has a direct route to an Internet Gateway (0.0.0.0/0 pointing to an IGW) in order to translate private IPs and forward traffic to the internet; without that route, the NAT Gateway itself cannot send or receive internet-bound packets, even if the private subnet’s route table correctly points to the NAT Gateway. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this question tests your understanding of VPC routing dependencies and the layered connectivity model—a common trap is to focus only on the private subnet’s route table while overlooking the public subnet’s missing IGW route. Remember the memory tip: “NAT needs a path to the IGW first, or it’s just an expensive paperweight.”
SOA-C02 Networking and Content Delivery Practice Question
This SOA-C02 practice question tests your understanding of networking and content delivery. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 SysOps administrator is configuring a VPC with a public subnet and a private subnet. The private subnet needs to access the internet to download patches. The administrator creates a NAT Gateway in the public subnet and updates the private subnet route table. However, instances in the private subnet cannot reach the internet. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The route table for the public subnet does not have a route to an Internet Gateway.
The NATGateway must be in a public subnet with an Internet Gateway route. If the route table for the public subnet does not have a route to an Internet Gateway, the NAT Gateway cannot send traffic to the internet. Option A is incorrect because EIP is required for NAT Gateway. Option B is incorrect because security groups do not apply to NAT Gateway. Option D is incorrect because NACLs affect traffic but not the core issue.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The network ACL for the private subnet blocks outbound traffic.
Why it's wrong here
NACLs are stateless and may block, but the primary issue is likely routing.
✓
The route table for the public subnet does not have a route to an Internet Gateway.
Why this is correct
NATGateway needs Internet Gateway route to reach the internet.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SOA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Networking and Content Delivery — This question tests Networking and Content Delivery — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The route table for the public subnet does not have a route to an Internet Gateway. — The NAT Gateway must be in a public subnet with an Internet Gateway route. If the route table for the public subnet does not have a route to an Internet Gateway, the NAT Gateway cannot send traffic to the internet. Option A is incorrect because EIP is required for NAT Gateway. Option B is incorrect because security groups do not apply to NAT Gateway. Option D is incorrect because NACLs affect traffic but not the core issue.
What should I do if I get this SOA-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SOA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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. A SysOps administrator is troubleshooting internet connectivity for an EC2 instance in subnet subnet-0a1b2c3d4e5f6g7h8. The instance can reach other instances in the VPC but cannot access the internet. Based on the route table output, what is the most likely cause?
hard
A.The default route (0.0.0.0/0) is missing
B.The route table is not associated with the subnet
✓ C.The NAT gateway does not have a route to an internet gateway
D.The VPC CIDR route is misconfigured
Why C: Option C is correct because the route table has a default route to a NAT gateway, but the exhibit does not show that the NAT gateway is in a public subnet with an internet gateway route. If the NAT gateway lacks internet access, private instances cannot reach the internet. Option A is wrong because the route table is associated with the subnet. Option B is wrong because the route exists. Option D is wrong because the VPC CIDR is local, which is fine.
Last reviewed: Jun 20, 2026
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This SOA-C02 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 SOA-C02 exam.
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