Question 1,483 of 318
Enable Outbound Internet Access While Blocking Inbound Traffic with NAT Gateway
A security engineer is designing a VPC with public and private subnets. The application servers in the private subnets need to access the internet for software updates, but must not be directly reachable from the internet. Which TWO actions satisfy these requirements?
Quick Answer
The answer is deploying a NAT gateway in a public subnet. This satisfies the requirement because a NAT gateway, placed in a public subnet with an Elastic IP and a route to an internet gateway, allows instances in private subnets to initiate outbound internet connections—such as for software updates—while the gateway’s stateful firewall automatically drops any unsolicited inbound traffic from the internet. The private subnet’s route table must have a default route (0.0.0.0/0) pointing to the NAT gateway’s private IP to forward outbound traffic. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of how to enable outbound internet from private subnets using NAT gateway without exposing resources to inbound attacks. A common trap is confusing a NAT gateway with a NAT instance or assuming a public subnet is required for the private instances themselves. Memory tip: think “NAT out, never in”—the gateway only translates outbound requests, never unsolicited inbound ones.
⚠ Common exam trap
Many candidates confuse a NAT gateway with an internet gateway, mistakenly thinking that adding an internet gateway to a private subnet's route table provides outbound-only access, when in fact it enables bidirectional internet connectivity and requires public IPs on the instances.
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 route in the private subnet's route table pointing to the NAT gateway.
A NAT gateway, when deployed in a public subnet with an associated Elastic IP and a route to an internet gateway, allows instances in private subnets to initiate outbound connections 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's private IP address to forward outbound traffic through it.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure the private subnet's security group to allow inbound traffic from 0.0.0.0/0.
Why it's wrong here
Incorrect: This would allow inbound internet traffic directly to instances.
- ✓
Add a route in the private subnet's route table pointing to the NAT gateway.
Why this is correct
Correct: This routes outbound internet traffic through the NAT gateway.
- ✗
Attach an internet gateway to the private subnet's route table.
Why it's wrong here
Incorrect: This would make the private subnet public, allowing inbound traffic.
- ✗
Create a VPC gateway endpoint for Amazon S3.
Why it's wrong here
Incorrect: VPC endpoints provide access to specific AWS services, not general internet.
- ✓
Deploy a NAT gateway in a public subnet.
Why this is correct
Correct: NAT gateway enables outbound internet access from private subnets.
Visual reference
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Same concept, more angles
1 more way this is tested on SCS-C02
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 security engineer is configuring a new VPC with public and private subnets. The application servers in the private subnet need to download patches from the internet. Which component is required?
easy- A.VPC endpoint
- B.Direct Connect
- C.Internet gateway
- ✓ D.NAT gateway
Why D: A NAT gateway is required to allow instances in a private subnet to initiate outbound traffic to the internet (e.g., to download patches) while preventing the internet from initiating inbound connections to those instances. The NAT gateway resides in a public subnet with an attached Internet Gateway, and it translates the private IP addresses of the application servers to the NAT gateway's Elastic IP address for outbound traffic.
Last reviewed: Jun 11, 2026
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.
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