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 company has a VPC with public and private subnets. A NAT Gateway is deployed in the public subnet. Private EC2 instances need to download patches from the internet. The route table for the private subnet has a default route (0.0.0.0/0) pointing to the NAT Gateway. However, the instances 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 NAT Gateway is not placed in a public subnet with a route to an internet gateway.
Option C is correct because the NAT Gateway must be in a public subnet with an internet gateway route. If the NAT Gateway's subnet's route table does not have a default route to an internet gateway, the NAT Gateway cannot forward traffic to the internet. Option A is wrong because the NAT Gateway does not need a public IP for outbound-only traffic (though it helps). Option B is irrelevant to internet access. Option D is wrong because security groups for private instances should allow outbound traffic.
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 private subnet’s network ACL is blocking outbound traffic.
Why it's wrong here
Network ACLs are stateless; default NACL allows all outbound.
✓
The NAT Gateway is not placed in a public subnet with a route to an internet gateway.
Why this is correct
NATGateway must be in a public subnet with IGW route to translate and forward traffic.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The security group for the private instances does not allow outbound HTTPS.
Why it's wrong here
Security groups are stateful; outbound rules are not typically an issue for established connections.
✗
The NAT Gateway does not have an Elastic IP address assigned.
Why it's wrong here
A NATGateway requires an Elastic IP to communicate with the internet.
Common exam traps
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 NAT Gateway is not placed in a public subnet with a route to an internet gateway. — Option C is correct because the NAT Gateway must be in a public subnet with an internet gateway route. If the NAT Gateway's subnet's route table does not have a default route to an internet gateway, the NAT Gateway cannot forward traffic to the internet. Option A is wrong because the NAT Gateway does not need a public IP for outbound-only traffic (though it helps). Option B is irrelevant to internet access. Option D is wrong because security groups for private instances should allow outbound traffic.
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.
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