The correct answer is to assign an Amazon-provided IPv6 CIDR block to the VPC and subnets, then create an Egress-Only Internet Gateway for outbound traffic. This is the simplest and most standard method to enable IPv6 in a VPC because IPv6 addresses are globally unique and do not require NAT or private-to-public translation; an Egress-Only Internet Gateway allows outbound-only IPv6 communication while preventing inbound connections initiated from the internet, mirroring the security model of a NAT Gateway but for the IPv6 protocol. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your understanding that NAT Gateways are IPv4-only and that IPv6 inherently avoids NAT, making options involving NAT or VPN for internet access incorrect traps. A common pitfall is confusing IPv6 egress requirements with IPv4 patterns—remember, for IPv6, think “egress-only, not NAT.” Memory tip: “IPv6 is public by default, so just let it out, don’t hide it.”
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 of 10.0.0.0/16. They need to add IPv6 support for their application. What is the simplest way to enable IPv6 communication for instances in the VPC?
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 create an Egress-Only Internet Gateway for outbound traffic.
Option A is correct because assigning an IPv6 CIDR to the VPC and subnet, and using an Egress-Only Internet Gateway for outbound, is the standard method. Option B is wrong because NAT Gateways are IPv4-only. Option C is wrong because IPv6 does not use NAT. Option D is wrong because VPN does not provide IPv6 internet access.
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.
✓
Assign an Amazon-provided IPv6 CIDR block to the VPC and subnets, and create an Egress-Only Internet Gateway for outbound traffic.
Use an Internet Gateway with NAT for IPv6 traffic.
Why it's wrong here
Wrong: Internet Gateway supports IPv6 but NAT is not needed.
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.
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: Assign an Amazon-provided IPv6 CIDR block to the VPC and subnets, and create an Egress-Only Internet Gateway for outbound traffic. — Option A is correct because assigning an IPv6 CIDR to the VPC and subnet, and using an Egress-Only Internet Gateway for outbound, is the standard method. Option B is wrong because NAT Gateways are IPv4-only. Option C is wrong because IPv6 does not use NAT. Option D is wrong because VPN does not provide IPv6 internet access.
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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Question Discussion
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