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Infrastructure Security →mediumMultiple ChoiceObjective-mapped

SCS-C02 Infrastructure Security Practice Question

This SCS-C02 practice question tests your understanding of infrastructure security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 notices that an EC2 instance in a private subnet is able to make outbound connections to the internet. The instance does not have a public IP, and there is no NAT gateway or instance in the VPC. 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.

A
The VPC has an egress-only internet gateway for IPv6 traffic.
Correct. An egress-only internet gateway supports outbound IPv6 traffic from private subnets, enabling internet connectivity without a public IP.
B
The instance has a public IP assigned automatically via Auto-assign Public IP.
Why wrong: The question states no public IP.
C
The instance is using a VPC endpoint (Gateway type) for S3.
Why wrong: A VPC endpoint for S3 only provides access to S3, not general internet.
D
The subnet's route table has a default route (0.0.0.0/0) pointing to an internet gateway.
Why wrong: Incorrect. An internet gateway does not perform NAT; it requires instances to have public IP addresses for return traffic. Without a public IP or NAT device, a default route to an IGW cannot provide internet connectivity.

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

✓

The VPC has an egress-only internet gateway for IPv6 traffic.

Option A is correct because an egress-only internet gateway (EIGW) allows outbound IPv6 traffic from instances in a private subnet without requiring a public IPv4 address or NAT. Since the instance is making outbound connections to the internet and has no public IP or NAT, and the VPC likely has IPv6 enabled, the EIGW is the most plausible cause. Option D is incorrect because a default route to an internet gateway requires the instance to have a public IPv4 address for return traffic, which contradicts the scenario.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

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 VPC has an egress-only internet gateway for IPv6 traffic.
Why this is correct
Correct. An egress-only internet gateway supports outbound IPv6 traffic from private subnets, enabling internet connectivity without a public IP.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The instance has a public IP assigned automatically via Auto-assign Public IP.
Why it's wrong here
The question states no public IP.
✗
The instance is using a VPC endpoint (Gateway type) for S3.
Why it's wrong here
A VPC endpoint for S3 only provides access to S3, not general internet.
✗
The subnet's route table has a default route (0.0.0.0/0) pointing to an internet gateway.
Why it's wrong here
Incorrect. An internet gateway does not perform NAT; it requires instances to have public IP addresses for return traffic. Without a public IP or NAT device, a default route to an IGW cannot provide internet connectivity.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates assume a private subnet inherently blocks internet access, but the question tests whether they understand that a subnet's route table—not its public/private designation—determines outbound connectivity, and a 0.0.0.0/0 route to an IGW makes it a public subnet regardless of the instance's IP assignment.

Detailed technical explanation

How to think about this question

An internet gateway performs 1-to-1 NAT for instances with public IPs, but for instances without public IPs, a route to an IGW alone does not enable outbound connectivity unless the instance has a public IP or the subnet is public. In practice, if a private subnet has a 0.0.0.0/0 route to an IGW, the instance can send packets to the IGW, but the IGW will drop them because it has no mapping for a private IP; however, if the instance is in a public subnet (with a public IP), the IGW performs NAT. The key subtlety is that a 'private subnet' is defined by the absence of a direct route to an IGW, so the scenario implies a misconfiguration where the subnet is actually public.

KKey Concepts to Remember

Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.

TExam Day Tips

Watch for words such as best, first, most likely and least administrative effort.
Review why wrong options are wrong, not only why the correct option is correct.

Key takeaway

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

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

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this SCS-C02 question test?

Infrastructure Security — This question tests Infrastructure Security — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The VPC has an egress-only internet gateway for IPv6 traffic. — Option A is correct because an egress-only internet gateway (EIGW) allows outbound IPv6 traffic from instances in a private subnet without requiring a public IPv4 address or NAT. Since the instance is making outbound connections to the internet and has no public IP or NAT, and the VPC likely has IPv6 enabled, the EIGW is the most plausible cause. Option D is incorrect because a default route to an internet gateway requires the instance to have a public IPv4 address for return traffic, which contradicts the scenario.

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

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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?

Read the scenario before looking for a memorised answer.

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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.