- A
Attach an Internet Gateway to the private subnets
Why wrong: Internet Gateway allows bidirectional traffic, which is not desired.
- B
Deploy a NAT Gateway in a public subnet and update the private subnet route table
NAT Gateway provides outbound-only internet access for private instances.
- C
Set up a VPN connection to an on-premises network
Why wrong: VPN is for private connectivity, not internet access.
- D
Create a VPC endpoint for S3
Why wrong: VPC endpoints are for AWS services, not general internet access.
Question 368 of 1,705
Configuring NAT Gateway for Outbound-Only Internet Access
This ANS-C01 practice question tests your understanding of network implementation. 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 has a VPC with public and private subnets. The private subnets need to access the internet for software updates. The company wants to ensure that traffic can only go out to the internet and not be initiated from the internet. Which configuration should be used?
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
✓
Deploy a NAT Gateway in a public subnet and update the private subnet route table
A NAT Gateway deployed in a public subnet with an Elastic IP allows private subnet instances to initiate outbound traffic to the internet (e.g., for software updates) while preventing any unsolicited inbound connections from the internet. The private subnet’s route table must include a default route (0.0.0.0/0) pointing to the NAT Gateway, which translates the private source IP to the gateway’s Elastic IP for return traffic. This meets the requirement of outbound-only internet access without exposing private instances to inbound initiation.
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.
- ✗
Attach an Internet Gateway to the private subnets
Why it's wrong here
Internet Gateway allows bidirectional traffic, which is not desired.
- ✓
Deploy a NAT Gateway in a public subnet and update the private subnet route table
- ✗
Set up a VPN connection to an on-premises network
Why it's wrong here
VPN is for private connectivity, not internet access.
- ✗
Create a VPC endpoint for S3
Why it's wrong here
VPC endpoints are for AWS services, not general internet access.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse an Internet Gateway with a NAT Gateway, assuming both provide outbound-only access, but an Internet Gateway enables bidirectional traffic and requires public IPs on instances, while a NAT Gateway specifically allows outbound-only initiation from private instances.
Detailed technical explanation
How to think about this question
A NAT Gateway operates at Layer 4 (TCP/UDP) and performs source network address translation (SNAT), rewriting the source IP of outbound packets to its own Elastic IP and tracking state in a connection table so return packets are correctly forwarded back to the private instance. Unlike a NAT instance, a NAT Gateway is managed by AWS, automatically scales up to 45 Gbps, and does not require patching or failover scripts. In a real-world scenario, if the private subnet needs to access multiple internet-based repositories (e.g., yum, apt, or Windows Update), the NAT Gateway’s single Elastic IP can be whitelisted in firewall rules, simplifying security group management.
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
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Deploy a NAT Gateway in a public subnet and update the private subnet route table — A NAT Gateway deployed in a public subnet with an Elastic IP allows private subnet instances to initiate outbound traffic to the internet (e.g., for software updates) while preventing any unsolicited inbound connections from the internet. The private subnet’s route table must include a default route (0.0.0.0/0) pointing to the NAT Gateway, which translates the private source IP to the gateway’s Elastic IP for return traffic. This meets the requirement of outbound-only internet access without exposing private instances to inbound initiation.
What should I do if I get this ANS-C01 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.
About these practice questions
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Same concept, more angles
2 more ways this is tested on ANS-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company has a VPC with a public subnet and a private subnet. An EC2 instance in the private subnet needs to download software patches from the internet. Which AWS service should be used to provide outbound internet access without allowing inbound traffic?
easy- A.Site-to-Site VPN connection
- B.VPC endpoint
- ✓ C.NAT gateway
- D.Internet gateway
Why C: A NAT gateway enables EC2 instances in a private subnet to initiate outbound IPv4 traffic to the internet (e.g., to download patches) while preventing any unsolicited inbound traffic from the internet. It resides in a public subnet with an Elastic IP and performs source network address translation (SNAT), replacing the private source IP with the gateway's public IP. This satisfies the requirement of outbound-only internet access without exposing the private instances to inbound connections.
Variation 2. A company has a VPC with a public subnet and a private subnet. They launch an EC2 instance in the private subnet with a private IP only. The instance needs to download patches from the internet. Which configuration is required?
medium- A.Launch a NAT instance in the private subnet and configure source/destination check.
- B.Create a VPC endpoint for the patch service.
- ✓ C.Create a NAT gateway in the public subnet and add a default route to the NAT gateway in the private subnet's route table.
- D.Attach an internet gateway to the VPC and add a default route to it in the private subnet's route table.
Why C: Option C is correct because a NAT gateway in the public subnet provides outbound internet access for instances in the private subnet while preventing inbound connections from the internet. By adding a default route (0.0.0.0/0) in the private subnet's route table pointing to the NAT gateway, traffic from the EC2 instance destined for the internet is forwarded to the NAT gateway, which then uses its Elastic IP to communicate with the internet. This allows the instance to download patches without requiring a public IP or direct internet gateway access.
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Last reviewed: Jul 4, 2026
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