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Infrastructure Security →hardMultiple ChoiceObjective-mapped

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 security engineer is troubleshooting connectivity issues from an EC2 instance in a private subnet to an S3 bucket. The instance has a security group allowing outbound HTTPS (443) to 0.0.0.0/0, and the subnet's network ACL allows outbound HTTPS to 0.0.0.0/0. However, requests to S3 are timing out. Which additional configuration is most likely required?

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.

A
Attach an IAM role to the EC2 instance with S3 permissions
Why wrong: Attaching an IAM role provides permissions for S3 actions but does not resolve connectivity issues; connectivity requires a network path.
B
Modify the security group to allow traffic to the S3 region-specific IP range
Why wrong: Modifying the security group to allow traffic to S3 region-specific IP ranges is not feasible because S3 IP ranges change frequently and are not easily manageable; using a VPC endpoint is the proper solution.
C
Add a VPC Gateway Endpoint for S3 and update the route table
Option C is correct because S3 endpoints are accessed via a prefix list in route tables; without a VPC Gateway Endpoint for S3, traffic goes through a NAT Gateway or Internet Gateway, but the private subnet lacks a route to the internet.
D
Configure a TLS termination proxy
Why wrong: Configuring a TLS termination proxy is unnecessary because S3 supports HTTPS directly and the issue is network routing, not TLS termination.

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

✓

Add a VPC Gateway Endpoint for S3 and update the route table

Option C is correct because S3 endpoints are accessed via a prefix list in route tables; without a VPC Gateway Endpoint for S3, traffic goes through a NAT Gateway or Internet Gateway, but the private subnet lacks a route to the internet. Option A is wrong because S3 supports HTTPS without TLS termination. Option B is wrong because S3 is a global service and does not require a specific region endpoint configuration at the VPC level. Option D is wrong because S3 does not require an IAM role for connectivity; that is for access permissions.

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.

✗
Attach an IAM role to the EC2 instance with S3 permissions
Why it's wrong here
Attaching an IAM role provides permissions for S3 actions but does not resolve connectivity issues; connectivity requires a network path.
✗
Modify the security group to allow traffic to the S3 region-specific IP range
Why it's wrong here
Modifying the security group to allow traffic to S3 region-specific IP ranges is not feasible because S3 IP ranges change frequently and are not easily manageable; using a VPC endpoint is the proper solution.
✓
Add a VPC Gateway Endpoint for S3 and update the route table
Why this is correct
Option C is correct because S3 endpoints are accessed via a prefix list in route tables; without a VPC Gateway Endpoint for S3, traffic goes through a NAT Gateway or Internet Gateway, but the private subnet lacks a route to the internet.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
✗
Configure a TLS termination proxy
Why it's wrong here
Configuring a TLS termination proxy is unnecessary because S3 supports HTTPS directly and the issue is network routing, not TLS termination.

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 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.

Visual reference

Quick reference

AWS S3 Storage Class Comparison

Storage Class	Min Duration	Retrieval	Use Case
S3 Standard	None	Immediate	Frequently accessed data
S3 Standard-IA	30 days	Immediate	Infrequent access, rapid retrieval
S3 One Zone-IA	30 days	Immediate	Non-critical infrequent data
S3 Intelligent-Tiering	None	Immediate–hours	Unknown or changing access patterns
S3 Glacier Instant	90 days	Milliseconds	Archive with instant retrieval
S3 Glacier Flexible	90 days	Minutes–hours	Archive, flexible retrieval
S3 Glacier Deep Archive	180 days	Hours	Long-term compliance archive

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.

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FAQ

Questions learners often ask

What does this SCS-C02 question test?

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: Add a VPC Gateway Endpoint for S3 and update the route table — Option C is correct because S3 endpoints are accessed via a prefix list in route tables; without a VPC Gateway Endpoint for S3, traffic goes through a NAT Gateway or Internet Gateway, but the private subnet lacks a route to the internet. Option A is wrong because S3 supports HTTPS without TLS termination. Option B is wrong because S3 is a global service and does not require a specific region endpoint configuration at the VPC level. Option D is wrong because S3 does not require an IAM role for connectivity; that is for access permissions.

What should I do if I get this SCS-C02 question wrong?

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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