- A
In the egress VPC, add a route for 0.0.0.0/0 to the Transit Gateway.
Why wrong: This would create a routing loop; the egress VPC should not send internet traffic back to Transit Gateway.
- B
Create a VPN connection between each VPC and the Transit Gateway.
Why wrong: VPCs are already attached to Transit Gateway; no VPN needed.
- C
In the egress VPC, add a route for 0.0.0.0/0 to the internet gateway in the route table of the subnet containing the NAT Gateway.
This allows the NAT Gateway to reach the internet via the internet gateway.
- D
In each non-egress VPC, add a route for 0.0.0.0/0 to the Transit Gateway.
This sends all internet-bound traffic to the Transit Gateway, which forwards it to the egress VPC.
- E
In each non-egress VPC, delete the local route.
Why wrong: The local route (VPC CIDR) is required and cannot be deleted.
Quick Answer
The answer is to configure a default route of 0.0.0.0/0 pointing to the Transit Gateway in each non-egress VPC, and a default route of 0.0.0.0/0 pointing to the internet gateway in the egress VPC. This works because centralized internet egress via Transit Gateway funnels all outbound traffic from spoke VPCs into a single egress VPC, where a NAT Gateway translates private IPs before the traffic reaches the internet gateway. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of transitive routing and the distinction between spoke and egress VPC route tables. A common trap is assuming the egress VPC should route 0.0.0.0/0 back to the Transit Gateway, which would create a routing loop; instead, the egress VPC must point directly to the internet gateway. Remember the memory tip: “Spokes point to the hub, the hub points to the internet”—the Transit Gateway is the hub for spoke routes, but the egress VPC itself must bypass the hub for internet-bound traffic.
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. 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 is using AWS Transit Gateway to connect multiple VPCs and on-premises networks. The company wants to centralize internet egress for all VPCs through a single VPC that has a NAT Gateway and an internet gateway. Which TWO configurations are required to achieve this?
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
In the egress VPC, add a route for 0.0.0.0/0 to the internet gateway in the route table of the subnet containing the NAT Gateway.
To centralize internet egress, the NAT Gateway must be in the egress VPC. Other VPCs must route 0.0.0.0/0 to the Transit Gateway, which then forwards to the egress VPC. The egress VPC's route table must point 0.0.0.0/0 to the internet gateway. Option A is correct because the egress VPC needs a default route to the internet gateway. Option C is correct because other VPCs need a default route to the Transit Gateway. Option B is incorrect because the egress VPC should not route to the Transit Gateway for internet traffic. Option D is incorrect because you do not need a separate VPN. Option E is incorrect because you cannot delete the local route.
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.
- ✗
In the egress VPC, add a route for 0.0.0.0/0 to the Transit Gateway.
Why it's wrong here
This would create a routing loop; the egress VPC should not send internet traffic back to Transit Gateway.
- ✗
Create a VPN connection between each VPC and the Transit Gateway.
- ✓
In the egress VPC, add a route for 0.0.0.0/0 to the internet gateway in the route table of the subnet containing the NAT Gateway.
- ✓
In each non-egress VPC, add a route for 0.0.0.0/0 to the Transit Gateway.
- ✗
In each non-egress VPC, delete the local route.
Why it's wrong here
The local route (VPC CIDR) is required and cannot be deleted.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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 Design — This question tests Network Design — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: In the egress VPC, add a route for 0.0.0.0/0 to the internet gateway in the route table of the subnet containing the NAT Gateway. — To centralize internet egress, the NAT Gateway must be in the egress VPC. Other VPCs must route 0.0.0.0/0 to the Transit Gateway, which then forwards to the egress VPC. The egress VPC's route table must point 0.0.0.0/0 to the internet gateway. Option A is correct because the egress VPC needs a default route to the internet gateway. Option C is correct because other VPCs need a default route to the Transit Gateway. Option B is incorrect because the egress VPC should not route to the Transit Gateway for internet traffic. Option D is incorrect because you do not need a separate VPN. Option E is incorrect because you cannot delete the local route.
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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Same concept, more angles
1 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 is using AWS Transit Gateway to connect multiple VPCs and on-premises data centers. They want to centralize internet traffic through a single VPC that has an internet gateway. Which Transit Gateway feature should they enable?
medium- ✓ A.Transit Gateway route tables
- B.VPN attachments
- C.Multicast support
- D.IPsec acceleration
Why A: To centralize internet traffic through a single VPC with an internet gateway, you need to control the routing of traffic from other VPCs and on-premises networks. Transit Gateway route tables allow you to isolate or share routes between attachments, enabling you to create a default route (0.0.0.0/0) pointing to the centralized VPC's attachment. This ensures all outbound internet traffic from other VPCs is forwarded to the egress VPC, which then uses its internet gateway.
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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