The correct answer is to place a NAT Gateway in a public subnet and route the EC2 instance’s traffic through it. This configuration works because a NAT Gateway, residing in a public subnet with an Internet Gateway attached, allows the EC2 instance in a private subnet to initiate outbound connections to the internet for patching, while the gateway’s stateful nature automatically blocks any unsolicited inbound traffic from the internet. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of how to enforce least-privilege network access for EC2 patching without exposing the instance to inbound attacks—a common trap is confusing a NAT Gateway with an Internet Gateway, which would permit bidirectional traffic and violate the security requirement. Remember the memory tip: “NAT for outbound only, IGW for two-way open.”
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 wants to allow an EC2 instance in a VPC to download patches from the internet but block all other outbound traffic. Which configuration should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Place a NAT Gateway in a public subnet and route the EC2 instance's traffic through it
Option A is correct because a NATGateway in a public subnet allows outbound internet access while blocking inbound. Option B is wrong because an Internet Gateway directly attached would allow bidirectional traffic. Option C is wrong because a VPN does not provide internet access. Option D is wrong because VPC Peering 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.
✓
Place a NAT Gateway in a public subnet and route the EC2 instance's traffic through it
Use a Virtual Private Gateway and connect to a VPN
Why it's wrong here
This does not provide internet access.
✗
Attach an Internet Gateway and add a route 0.0.0.0/0 to the EC2 instance's route table
Why it's wrong here
This would also allow inbound traffic if not restricted.
✗
Use a VPC Peering connection to an external VPC with internet access
Why it's wrong here
VPC Peering does not provide internet access.
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 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: Place a NAT Gateway in a public subnet and route the EC2 instance's traffic through it — Option A is correct because a NAT Gateway in a public subnet allows outbound internet access while blocking inbound. Option B is wrong because an Internet Gateway directly attached would allow bidirectional traffic. Option C is wrong because a VPN does not provide internet access. Option D is wrong because VPC Peering 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.
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Question Discussion
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