ANS-C01 Network Design Practice Question
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?
⚠ Common exam trap
Test-takers frequently confuse the Internet Gateway (which supports both IPv4 and IPv6) with the need for a NAT-like device for IPv6, not realizing that IPv6 does not use NAT and that an Egress-Only Internet Gateway is the correct AWS service for outbound-only IPv6 access.
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 create an Egress-Only Internet Gateway for outbound traffic.
The simplest way to enable IPv6 communication in a VPC is to associate an Amazon-provided IPv6 CIDR block (a /56 from the 2002::/25 range) to the VPC and its subnets, then create an Egress-Only Internet Gateway (EIGW) for outbound-only IPv6 traffic. This allows instances with IPv6 addresses to initiate outbound connections to the internet while preventing inbound connections, which is the default security model for IPv6 in AWS.
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.
Why this is correct
Correct: Standard IPv6 enablement.
- ✗
Create a VPN connection to an external IPv6 network.
Why it's wrong here
Wrong: Does not enable IPv6 internet access.
- ✗
Configure a NAT Gateway in a public subnet and assign IPv6 addresses to instances.
Why it's wrong here
Wrong: NAT Gateway does not support IPv6.
- ✗
Use an Internet Gateway with NAT for IPv6 traffic.
Why it's wrong here
Wrong: Internet Gateway supports IPv6 but NAT is not needed.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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