The answer is to associate an IPv6 CIDR block with the VPC and subnets, then update route tables to route IPv6 traffic to an internet gateway. This is correct because an internet gateway natively supports both IPv4 and IPv6 traffic, acting as a dual-stack target for routes; once the VPC and subnets have an IPv6 CIDR assigned, adding a default route (::/0) pointing to the internet gateway enables inbound and outbound IPv6 communication. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this tests your understanding of VPC dual-stack architecture and the distinction between an internet gateway (bidirectional IPv6) and an egress-only internet gateway (outbound-only IPv6). A common trap is confusing the egress-only gateway for general internet access—remember, it blocks inbound IPv6 traffic. Memory tip: “IG for both ways, EIG for outbound 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 deploying an application that must use IPv6 for internet-facing traffic. The VPC is currently using IPv4 only. What is the simplest way to enable IPv6?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Associate an IPv6 CIDR block with the VPC and subnets, and update route tables to route IPv6 traffic to an internet gateway.
Option A is correct because you can assign an IPv6 CIDR block to the VPC and subnets, and then update route tables. Option B is wrong because a NAT device is for IPv4. Option C is wrong because an egress-only internet gateway is for outbound-only IPv6. Option D is wrong because a 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.
✗
Use an egress-only internet gateway for IPv6 traffic.
Why it's wrong here
Egress-only internet gateway is for outbound-only traffic; inbound traffic is not possible.
✓
Associate an IPv6 CIDR block with the VPC and subnets, and update route tables to route IPv6 traffic to an internet gateway.
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: Associate an IPv6 CIDR block with the VPC and subnets, and update route tables to route IPv6 traffic to an internet gateway. — Option A is correct because you can assign an IPv6 CIDR block to the VPC and subnets, and then update route tables. Option B is wrong because a NAT device is for IPv4. Option C is wrong because an egress-only internet gateway is for outbound-only IPv6. Option D is wrong because a 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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