NAT Gateway for Private Subnet Internet Access
A security engineer is configuring a VPC with public and private subnets. The engineer needs to allow instances in the private subnet to download software updates from the internet. Which component should be added to the VPC?
⚠ Common exam trap
SCS-C02 often tests the misconception that a VPC endpoint or bastion host can provide general outbound internet access; candidates must recognize that only a NAT device (gateway or instance) in a public subnet enables private-subnet instances to reach the internet.
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 in a public subnet.
A NAT gateway placed in a public subnet allows instances in a private subnet to initiate outbound connections to the internet (e.g., to download software updates) while remaining unreachable from the internet. The NAT gateway performs source NAT, translating the private IPs to its own Elastic IP, and returns responses to the originating instances. This is the standard AWS pattern for giving private subnets outbound-only internet access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
VPN connection to on-premises.
Why it's wrong here
A VPN connection to on-premises is incorrect because a Site-to-Site VPN creates an encrypted IPSec tunnel between your VPC and your on-premises network, enabling private, secure communication with your data center. It does not provide any general internet egress path; traffic destined for the internet would still need to traverse an internet gateway or NAT device. The VPN only reaches private IP ranges advertised from the on-premises side, not public internet destinations.
- ✗
VPC endpoint for Amazon S3.
Why it's wrong here
A VPC endpoint for Amazon S3 is incorrect for this use case because it provides private, highly available connectivity to S3 only, without traversing the public internet. It does not act as a general-purpose outbound internet gateway: any traffic to destinations other than S3 is not forwarded. Endpoints are service-specific and cannot route 0.0.0.0/0 traffic or handle web traffic to arbitrary public hosts.
- ✗
Bastion host in a public subnet.
Why it's wrong here
A bastion host in a public subnet is incorrect because its purpose is inbound administrative access (e.g., SSH or RDP) for engineers to reach instances in private subnets, not to provide outbound internet access for those instances. A bastion host does not perform NAT or packet forwarding by default, and even if configured, it would require additional routing and security group changes to function as a NAT instance. It is not a managed, scalable solution for general internet connectivity from private subnets.
- ✓
NAT gateway in a public subnet.
Why this is correct
A NAT gateway in a public subnet is correct because it enables instances in private subnets to initiate outbound IPv4 traffic to the internet, such as software updates or API calls, while preventing unsolicited inbound connections from reaching them. The NAT gateway resides in a public subnet with an Elastic IP and uses the internet gateway to reach external networks, while private subnet route tables direct 0.0.0.0/0 traffic to the NAT gateway. It is fully managed, scales automatically, and does not require patch management—unlike a NAT instance.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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.