- A
Attach a virtual private gateway to the central VPC and add a static route in the transit gateway route table pointing 0.0.0.0/0 to the virtual private gateway
The virtual private gateway can route to the NAT gateway via the central VPC's route tables, and the transit gateway propagates the route to other attachments.
- B
Add a default route in the central VPC's subnet route tables pointing to the internet gateway
Why wrong: This allows outbound traffic from the central VPC only, not from other VPCs.
- C
Create a route table in the central VPC and associate it with the transit gateway attachment
Why wrong: Transit gateway attachments do not have route tables; route tables are on the transit gateway itself.
- D
Add a route in the transit gateway route table pointing 0.0.0.0/0 to the NAT gateway in the central VPC
Why wrong: Transit gateway cannot route to a NAT gateway directly; it can route to a VPC attachment or a VPN attachment.
Quick Answer
The correct configuration requires attaching a virtual private gateway to the central VPC and adding a static route in the transit gateway route table pointing 0.0.0.0/0 to that virtual private gateway. This works because the transit gateway can route traffic to a virtual private gateway as a next hop, which then forwards it to the internet gateway and NAT gateway within the central VPC. All other VPCs simply need a default route in their route tables pointing to their transit gateway attachment, allowing centralized outbound internet traffic to flow through the single VPC. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of transit gateway route propagation and the distinction between route table attachments versus direct next-hop targets. A common trap is assuming the transit gateway can route directly to a NAT gateway or internet gateway—it cannot; it requires a virtual private gateway or a prefix list as an intermediary. Memory tip: think of the virtual private gateway as the “on-ramp” that the transit gateway uses to enter the central VPC’s internet path.
ANS-C01 Network Implementation Practice Question
This ANS-C01 practice question tests your understanding of network implementation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 an AWS Transit Gateway with multiple VPC attachments. They want to centralize outbound internet traffic through a single VPC that has a NAT gateway and an internet gateway. All other VPCs should route internet-bound traffic through this central VPC. What configuration is required?
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
Attach a virtual private gateway to the central VPC and add a static route in the transit gateway route table pointing 0.0.0.0/0 to the virtual private gateway
Option D is correct because you need to attach a virtual private gateway to the central VPC and add a static route in the transit gateway route table pointing 0.0.0.0/0 to that VGW, then the other VPCs need a default route in their route tables pointing to the transit gateway attachment. Option A is wrong because TGW attachments do not have route tables; route tables are associated with TGW. Option B is wrong because that would send traffic directly to the internet gateway, not through the central VPC. Option C is wrong because that would route traffic to the NAT gateway directly in the central VPC, but the transit gateway cannot route to a NAT gateway directly; it needs a VGW or a prefix list.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 a virtual private gateway to the central VPC and add a static route in the transit gateway route table pointing 0.0.0.0/0 to the virtual private gateway
- ✗
Add a default route in the central VPC's subnet route tables pointing to the internet gateway
Why it's wrong here
This allows outbound traffic from the central VPC only, not from other VPCs.
- ✗
Create a route table in the central VPC and associate it with the transit gateway attachment
Why it's wrong here
Transit gateway attachments do not have route tables; route tables are on the transit gateway itself.
- ✗
Add a route in the transit gateway route table pointing 0.0.0.0/0 to the NAT gateway in the central VPC
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Attach a virtual private gateway to the central VPC and add a static route in the transit gateway route table pointing 0.0.0.0/0 to the virtual private gateway — Option D is correct because you need to attach a virtual private gateway to the central VPC and add a static route in the transit gateway route table pointing 0.0.0.0/0 to that VGW, then the other VPCs need a default route in their route tables pointing to the transit gateway attachment. Option A is wrong because TGW attachments do not have route tables; route tables are associated with TGW. Option B is wrong because that would send traffic directly to the internet gateway, not through the central VPC. Option C is wrong because that would route traffic to the NAT gateway directly in the central VPC, but the transit gateway cannot route to a NAT gateway directly; it needs a VGW or a prefix list.
What should I do if I get this ANS-C01 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Last reviewed: Jun 20, 2026
This ANS-C01 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 ANS-C01 exam.
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