- A
Assign an Amazon-provided IPv6 CIDR block to the VPC and subnets, and update route tables to use an internet gateway for IPv6
The internet gateway supports both IPv4 and IPv6; route tables can direct IPv6 traffic to it.
- B
Create a transit gateway and attach the VPC, then route IPv6 traffic through a VPN
Why wrong: Transit gateway is not needed for internet connectivity.
- C
Create a NAT Gateway in a public subnet and route IPv6 traffic through it
Why wrong: NAT Gateways are for IPv4 only.
- D
Assign an IPv6 CIDR to the VPC and subnets, and add an egress-only internet gateway
Why wrong: Egress-only internet gateway is for outbound only; internet-facing apps need inbound.
Question 38 of 1,705
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 has a VPC with an IPv4 CIDR block of 10.0.0.0/16. They need to add IPv6 connectivity for their internet-facing applications. The VPC currently has an internet gateway attached. What is the MOST efficient way to enable IPv6?
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
✓
Assign an Amazon-provided IPv6 CIDR block to the VPC and subnets, and update route tables to use an internet gateway for IPv6
Option A is correct because the most efficient way to enable IPv6 for an existing VPC with an internet gateway is to request an Amazon-provided IPv6 CIDR block (a /56 block) for the VPC, assign a /64 IPv6 CIDR to each subnet, and then update the route tables to direct ::/0 traffic to the internet gateway. The internet gateway is a dual-stack resource that inherently supports both IPv4 and IPv6 traffic, so no additional gateway is needed for outbound-only or inbound IPv6 connectivity.
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.
- ✓
Assign an Amazon-provided IPv6 CIDR block to the VPC and subnets, and update route tables to use an internet gateway for IPv6
Why this is correct
The internet gateway supports both IPv4 and IPv6; route tables can direct IPv6 traffic to it.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Create a transit gateway and attach the VPC, then route IPv6 traffic through a VPN
Why it's wrong here
Transit gateway is not needed for internet connectivity.
- ✗
Create a NAT Gateway in a public subnet and route IPv6 traffic through it
Why it's wrong here
NAT Gateways are for IPv4 only.
- ✗
Assign an IPv6 CIDR to the VPC and subnets, and add an egress-only internet gateway
Why it's wrong here
Egress-only internet gateway is for outbound only; internet-facing apps need inbound.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the misconception that an egress-only internet gateway is required for all IPv6 traffic, but the trap here is that an egress-only internet gateway is only for outbound-only scenarios, whereas internet-facing applications need bidirectional IPv6 traffic, which requires a standard internet gateway.
Detailed technical explanation
How to think about this question
When you associate an Amazon-provided IPv6 CIDR with a VPC, AWS automatically assigns a /56 block from the global unicast address space (2002::/16 for AWS, but typically 2600:1f14::/32 or similar). Each subnet receives a /64 prefix, and the internet gateway performs 1:1 NAT for IPv6 (no PAT), meaning each instance receives a globally unique IPv6 address. Route tables must have a default route (::/0) pointing to the internet gateway for both inbound and outbound IPv6 traffic; unlike IPv4, there is no need for a separate NAT device because IPv6 addresses are public by default.
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 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.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Assign an Amazon-provided IPv6 CIDR block to the VPC and subnets, and update route tables to use an internet gateway for IPv6 — Option A is correct because the most efficient way to enable IPv6 for an existing VPC with an internet gateway is to request an Amazon-provided IPv6 CIDR block (a /56 block) for the VPC, assign a /64 IPv6 CIDR to each subnet, and then update the route tables to direct ::/0 traffic to the internet gateway. The internet gateway is a dual-stack resource that inherently supports both IPv4 and IPv6 traffic, so no additional gateway is needed for outbound-only or inbound IPv6 connectivity.
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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Last reviewed: Jun 30, 2026
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