Quick Answer
The answer is to attach an internet gateway and update the route tables for IPv6. This is correct because an internet gateway is a horizontally scaled, redundant, and highly available VPC component that allows communication between your VPC and the internet, and it inherently supports both IPv4 and IPv6 traffic. When you add an IPv6 CIDR block to a VPC, you must create a new route in the route table pointing the destination ::/0 to the internet gateway ID, enabling bidirectional traffic for IPv6-enabled resources. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of dual-stack networking and the distinct roles of gateways—a common trap is confusing an egress-only internet gateway (which blocks inbound IPv6) with a standard internet gateway, or mistakenly selecting a NAT gateway, which only handles outbound IPv4. Remember the memory tip: for full IPv6 internet access, think “IGW + ::/0 route,” and never use a NAT gateway for IPv6.
This ANS-C01 practice question tests your understanding of network implementation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 an IPv6 CIDR block and ensure that traffic from the internet to the IPv6-enabled resources is allowed. Which configuration is required?
Attach a NAT gateway to the VPC and update route tables.
Why wrong: NAT gateway is for IPv4 outbound.
Attach an internet gateway and update route tables for IPv6.
IGW supports IPv6 traffic.
Create a Virtual Private Gateway and attach the VPC.
Why wrong: VPG is for hybrid connectivity.
Create a Transit Gateway and attach the VPC.
Why wrong: TGW is for internal routing.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Attach an internet gateway and update route tables for IPv6.
Option B is correct because an internet gateway must be attached to the VPC and must be IPv6-compatible (allows egress-only or full dual-stack). Option A is incorrect because a NAT gateway is for outbound IPv4. Option C is incorrect because a Transit Gateway is for inter-VPC connectivity. Option D is incorrect because a Virtual Private Gateway is for VPN/Direct Connect.
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
For each option: why learners choose it and why it is or isn't the right answer here.
Attach a NAT gateway to the VPC and update route tables.
Attach an internet gateway and update route tables for IPv6.
Why this is correct
IGW supports IPv6 traffic.
Related concept
CIDR notation defines the prefix length.
Create a Virtual Private Gateway and attach the VPC.
Why it's wrong here
VPG is for hybrid connectivity.
Create a Transit Gateway and attach the VPC.
Why it's wrong here
TGW is for internal routing.
Common exam traps
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
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.
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
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
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
Network Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
The correct answer is: Attach an internet gateway and update route tables for IPv6. — Option B is correct because an internet gateway must be attached to the VPC and must be IPv6-compatible (allows egress-only or full dual-stack). Option A is incorrect because a NAT gateway is for outbound IPv4. Option C is incorrect because a Transit Gateway is for inter-VPC connectivity. Option D is incorrect because a Virtual Private Gateway is for VPN/Direct Connect.
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.
CIDR notation defines the prefix length.
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Last reviewed: Jun 20, 2026
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