- A
Virtual Private Gateway
Why wrong: A Virtual Private Gateway is used for VPN connections to on-premises networks.
- B
VPC Peering Connection
Why wrong: VPC Peering connects VPCs but does not provide internet access.
- C
Internet Gateway
Why wrong: An Internet Gateway allows both inbound and outbound internet access, making instances reachable from the internet.
- D
NAT Gateway
A NAT Gateway allows outbound internet traffic from private subnets while blocking inbound traffic.
Question 1,634 of 1,705
NAT Gateway for Private Subnet Internet Access
This ANS-C01 practice question tests your understanding of network implementation. 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 company is deploying a VPC with public and private subnets across two Availability Zones. They need to ensure that instances in the private subnets can access the internet for software updates without being directly reachable from the internet. Which AWS service should they use?
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 private subnets to initiate outbound traffic to the internet (e.g., for software updates) while preventing unsolicited inbound connections from the internet. It translates the private IP addresses of the instances to the NAT Gateway's Elastic IP address using source network address translation (SNAT). This satisfies the requirement of internet access without direct reachability.
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.
- ✗
Virtual Private Gateway
- ✗
VPC Peering Connection
Why it's wrong here
VPC Peering connects VPCs but does not provide internet access.
- ✗
Internet Gateway
Why it's wrong here
An Internet Gateway allows both inbound and outbound internet access, making instances reachable from the internet.
- ✓
NAT Gateway
Common exam traps
Common exam trap: answer the scenario, not the keyword
The ANS-C01 exam often tests the misconception that an Internet Gateway can be used for private subnets by simply not assigning public IPs, but the trap here is that an Internet Gateway requires instances to have public IP addresses or Elastic IPs for outbound traffic, which still makes them potentially reachable from the internet if routes are misconfigured.
Detailed technical explanation
How to think about this question
A NAT Gateway operates at the network layer (Layer 3) and maintains stateful connections, meaning it tracks the source and destination IP/port pairs for outbound traffic and only allows return traffic that matches an existing session. It supports TCP, UDP, and ICMP protocols, and can handle up to 45 Gbps of bandwidth per Availability Zone. In a real-world scenario, if the NAT Gateway fails, all outbound internet traffic from private subnets in that AZ is disrupted unless a highly available setup with one NAT Gateway per AZ is deployed.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Visual reference
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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: NAT Gateway — A NAT Gateway enables instances in private subnets to initiate outbound traffic to the internet (e.g., for software updates) while preventing unsolicited inbound connections from the internet. It translates the private IP addresses of the instances to the NAT Gateway's Elastic IP address using source network address translation (SNAT). This satisfies the requirement of internet access without direct reachability.
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.
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Same concept, more angles
3 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 public and private subnets across two Availability Zones. The private subnets require outbound internet access for updates, but must not be directly reachable from the internet. The company has a NAT gateway in each public subnet. Security team reports that instances in private subnets cannot reach the internet. Which configuration should be verified first?
hard- ✓ A.Verify that the route table for the public subnets has a default route pointing to an internet gateway, and the private subnets' route table has a default route pointing to the NAT gateway
- B.Verify that the VPC has a VPC endpoint for S3 configured
- C.Verify that the network ACLs for the private subnets allow outbound traffic to 0.0.0.0/0
- D.Verify that the security groups attached to the instances allow outbound HTTPS traffic
Why A: Option A is correct because for instances in private subnets to reach the internet via a NAT gateway, the private subnet's route table must have a default route (0.0.0.0/0) pointing to the NAT gateway, and the NAT gateway must be placed in a public subnet whose route table has a default route pointing to an internet gateway. If either route is missing, outbound internet access will fail. Option B is incorrect because VPC endpoints are for accessing specific AWS services (e.g., S3), not general internet access. Option C is incorrect because NACLs are stateless and by default allow all outbound traffic; although custom NACLs could block traffic, routing misconfiguration is a more common first issue. Option D is incorrect because security groups are stateful and outbound traffic is allowed by default; blocking outbound HTTPS would be an intentional change, not the first thing to verify.
Variation 2. Which THREE actions are required to enable an EC2 instance in a private subnet to download software updates from the internet? (Select THREE.)
medium- A.Allocate an Elastic IP and associate it with the NAT Gateway
- B.Configure the security group to allow outbound traffic to 0.0.0.0/0
- ✓ C.Create a NAT Gateway in a public subnet
- ✓ D.Add a route in the private subnet route table pointing to the NAT Gateway for 0.0.0.0/0
- ✓ E.Attach an Internet Gateway to the VPC
Why C: To enable an EC2 instance in a private subnet to download software updates from the internet, you need a NAT Gateway in a public subnet (Option C) which requires an Internet Gateway attached to the VPC (Option E) to route traffic to the internet. Additionally, the private subnet's route table must have a default route (0.0.0.0/0) pointing to the NAT Gateway (Option D). While a NAT Gateway does require an Elastic IP, this is automatically allocated and associated during creation, so it is not a separate action.
Variation 3. A company is migrating a legacy application that requires static IP addresses for its clients' firewall whitelisting. The application will be hosted on EC2 instances behind a Network Load Balancer (NLB) in a private subnet. Which approach should the company use to provide static IP addresses for outbound traffic?
medium- A.Assign Elastic IPs to the EC2 instances
- B.Use an internet-facing NLB with Elastic IPs
- C.Use a VPC endpoint for the application
- ✓ D.Deploy a NAT Gateway in a public subnet with an Elastic IP
Why D: A NAT Gateway in a public subnet with an Elastic IP provides a static source IP address for outbound traffic from private subnets. Since the EC2 instances are in a private subnet behind an NLB, they cannot directly reach the internet; the NAT Gateway translates their private IPs to the Elastic IP, which clients can whitelist. This ensures consistent outbound IPs without exposing the instances to inbound traffic.
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Last reviewed: Jul 4, 2026
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