- A
Internet Gateway
Why wrong: An Internet Gateway enables both inbound and outbound internet connectivity — resources with public IPs can receive inbound connections from the internet.
- B
NAT Gateway
NAT Gateway in a public subnet allows private subnet instances to initiate outbound internet connections while dropping all unsolicited inbound connections — one-way internet access for private resources.
- C
Security Groups
Why wrong: Security groups are stateful firewalls that filter traffic based on rules — while they can block inbound traffic, the specific function of translating private IPs for outbound internet access is the NAT Gateway's role.
- D
Network ACLs
Why wrong: NACLs filter traffic at the subnet boundary — while they can block inbound traffic, they don't provide NAT translation for outbound internet access from private subnets.
Quick Answer
The answer is a NAT Gateway, because it is the AWS networking feature that enables resources in a private subnet to initiate outbound connections to the internet—for tasks like downloading patches or accessing external APIs—while blocking any unsolicited inbound connections from the internet. It works by translating the private IP addresses of the instances to the NAT Gateway’s Elastic IP for outbound traffic, and only forwarding return packets that belong to an already established session. On the AWS Certified Cloud Practitioner CLF-C02 exam, this distinction between NAT Gateway and Internet Gateway is a frequent trap: an Internet Gateway allows both inbound and outbound traffic, but only when attached to a public subnet, whereas a NAT Gateway is the correct choice for private subnet outbound internet access. A helpful memory tip is to think of the “N” in NAT as standing for “No inbound”—it only lets traffic out, never in.
CLF-C02 Security and Compliance Practice Question
This CLF-C02 practice question tests your understanding of security and compliance. 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.
Which AWS networking feature prevents resources in a private subnet from directly receiving inbound connections from the internet, while still allowing them to initiate outbound connections?
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
NAT Gateway
A NAT Gateway enables instances in a private subnet to initiate outbound connections to the internet (e.g., for software updates) while preventing any unsolicited inbound connections from the internet. It achieves this by translating the private IP of the instance to the NAT Gateway's Elastic IP for outbound traffic, and only forwarding return traffic that matches an established outbound session.
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.
- ✗
Internet Gateway
- ✓
NAT Gateway
- ✗
Security Groups
- ✗
Network ACLs
Why it's wrong here
NACLs filter traffic at the subnet boundary — while they can block inbound traffic, they don't provide NAT translation for outbound internet access from private subnets.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse a NAT Gateway with an Internet Gateway, assuming both provide internet access, but the key distinction is that an Internet Gateway allows bidirectional inbound connections, while a NAT Gateway specifically prevents unsolicited inbound connections from the internet.
Detailed technical explanation
How to think about this question
A NAT Gateway uses port address translation (PAT) to map multiple private IP addresses to a single Elastic IP, tracking each session in a connection table. It only forwards inbound traffic that is part of an already-established outbound connection (e.g., a response to an HTTP request), dropping any unsolicited inbound SYN packets. In a real-world scenario, if an EC2 instance in a private subnet needs to download patches from the internet, the NAT Gateway translates its source IP and port, and the response is matched to the existing session, ensuring the instance remains unreachable from the internet.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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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Security and Compliance — study guide chapter
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FAQ
Questions learners often ask
What does this CLF-C02 question test?
Security and Compliance — This question tests Security and Compliance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: NAT Gateway — A NAT Gateway enables instances in a private subnet to initiate outbound connections to the internet (e.g., for software updates) while preventing any unsolicited inbound connections from the internet. It achieves this by translating the private IP of the instance to the NAT Gateway's Elastic IP for outbound traffic, and only forwarding return traffic that matches an established outbound session.
What should I do if I get this CLF-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This CLF-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 CLF-C02 exam.
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