The correct choice is to attach all VPCs to a transit gateway and route traffic through a shared services VPC that has a NAT gateway and internet gateway. This architecture works because a transit gateway enables transitive routing between many VPCs, allowing a single centralized internet egress point in a multi-account environment to handle all outbound traffic. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of how to design scalable, centralized internet egress for multi-account architectures without relying on non-transitive VPC peering or unnecessary VPN connections. A common trap is assuming VPC peering can achieve transitive routing—it cannot, as each peering connection is one-to-one. Remember the memory tip: “Transit Gateway for transitive traffic; peering is point-to-point only.”
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. 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 designing a multi-account AWS environment using AWS Organizations. The company wants to centralize outbound internet traffic from all VPCs in all accounts through a single VPC in a shared services account. The shared services account has a VPC with a NAT gateway and an internet gateway. Which architecture meets this requirement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Attach all VPCs to a transit gateway and route traffic through a shared services VPC that has NAT gateway and internet gateway.
Option B is correct because a transit gateway with a default route to the shared services VPC and a NAT gateway there provides centralized outbound internet access. Option A is incorrect because VPC peering does not support transitive routing. Option C is incorrect because a VPN connection is not needed. Option D is incorrect because VPC endpoints are for specific services, not general internet.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Create VPC gateway endpoints for all AWS services in each VPC.
Why it's wrong here
Gateway endpoints do not provide general internet access.
✗
Set up a VPN connection from each VPC to the shared services VPC and use the latter's internet gateway.
Attach all VPCs to a transit gateway and route traffic through a shared services VPC that has NAT gateway and internet gateway.
Why this is correct
Transit gateway enables transitive routing and centralized internet.
Related concept
Static NAT maps one inside address to one outside address.
✗
Peer each VPC to the shared services VPC and configure a default route pointing to the shared services VPC's NAT gateway.
Why it's wrong here
VPC peering does not support transitive routing.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related ANS-C01 NAT questions on configuration and troubleshooting.
Network Design — This question tests Network Design — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Attach all VPCs to a transit gateway and route traffic through a shared services VPC that has NAT gateway and internet gateway. — Option B is correct because a transit gateway with a default route to the shared services VPC and a NAT gateway there provides centralized outbound internet access. Option A is incorrect because VPC peering does not support transitive routing. Option C is incorrect because a VPN connection is not needed. Option D is incorrect because VPC endpoints are for specific services, not general internet.
What should I do if I get this ANS-C01 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related ANS-C01 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
About these practice questions
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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 is designing a network for a multi-account AWS environment using AWS Organizations. The company must centralize internet egress for all accounts. Which TWO solutions should the company use? (Choose two.)
medium
A.Use VPC Peering to connect all VPCs to the egress VPC.
B.Deploy a AWS Client VPN endpoint in each VPC.
✓ C.Use AWS Transit Gateway to route traffic from all VPCs to the egress VPC.
D.Attach an Internet Gateway to each VPC and allow direct internet access.
✓ E.Create a centralized egress VPC with a NAT Gateway and Internet Gateway.
Why C: Option C is correct because AWS Transit Gateway acts as a central hub, enabling transitive routing between all attached VPCs. This allows traffic from multiple VPCs to be routed to a centralized egress VPC without requiring complex peering relationships or full mesh connectivity.
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Question Discussion
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