The correct choice is to configure private subnets with a NAT Gateway in a public subnet, as this setup allows outbound internet access for tasks like software updates while blocking any direct inbound connections from the internet. A NAT Gateway, placed in a public subnet with an Internet Gateway, translates private IP addresses to the gateway’s public IP for outbound traffic, but it does not accept unsolicited inbound traffic, thereby satisfying the security requirement. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of VPC traffic flow and subnet isolation, often appearing in multi-tier architecture questions where you must distinguish between public, private, and isolated subnets. A common trap is confusing isolated subnets (which have no route to the internet at all) with private subnets; remember that private subnets can reach the internet outbound via NAT, but isolated subnets cannot. Memory tip: NAT = “Not Allowed Inbound” — it only lets traffic out, never in.
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure security. 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 is designing a network architecture for a multi-tier web application. The application consists of a public-facing ALB, web servers in private subnets, and an RDS database in isolated subnets. The security team requires that the web servers have no direct internet access. Which VPC configuration meets this requirement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Private subnets with a NAT Gateway in a public subnet.
Option B is correct because private subnets with a NATGateway allow outbound internet access for updates while preventing inbound internet traffic. Option A is wrong because public subnets have direct internet access. Option C is wrong because isolated subnets cannot access the internet even for updates. Option D is wrong because a VPN does not provide internet access.
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.
✗
Public subnets with an Internet Gateway.
Why it's wrong here
Public subnets allow inbound internet traffic.
✗
Isolated subnets with no route to the internet.
Why it's wrong here
Isolated subnets cannot access internet for updates.
✓
Private subnets with a NAT Gateway in a public subnet.
Why this is correct
Private subnets have no direct inbound internet, but NAT enables outbound.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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 SCS-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Infrastructure Security — This question tests Infrastructure Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Private subnets with a NAT Gateway in a public subnet. — Option B is correct because private subnets with a NAT Gateway allow outbound internet access for updates while preventing inbound internet traffic. Option A is wrong because public subnets have direct internet access. Option C is wrong because isolated subnets cannot access the internet even for updates. Option D is wrong because a VPN does not provide internet access.
What should I do if I get this SCS-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 SCS-C02 subnetting questions on CIDR, address ranges, and subnet selection.
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 →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This SCS-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 SCS-C02 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.