ANS-C01 Network Implementation Practice Question
A company has a VPC with an IPv4 CIDR of 10.0.0.0/16 and needs to add IPv6 support for its public-facing web application. The application must be accessible via both IPv4 and IPv6. The VPC already has an Internet Gateway attached. What is the correct set of steps to enable IPv6?
⚠ Common exam trap
It's easy for candidates to confuse the need for an Egress-Only Internet Gateway with public-facing IPv6 access, but for inbound traffic, the regular Internet Gateway works for both IPv4 and 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
✓
Associate an Amazon-provided IPv6 CIDR block to the VPC, add a route for ::/0 to the Internet Gateway, and allocate IPv6 addresses to the subnets.
To enable IPv6 in a VPC, you must associate an Amazon-provided IPv6 CIDR block (a /56 block by default), add a route for the IPv6 default route (::/0) to the Internet Gateway, and allocate IPv6 addresses to the subnets. The Internet Gateway already supports IPv6 traffic natively, so no additional gateway is required for public-facing IPv6 access.
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 a custom IPv6 CIDR block from your own range to the VPC and add a route to the Internet Gateway.
Why it's wrong here
Custom IPv6 CIDR requires requesting from AWS.
- ✓
Associate an Amazon-provided IPv6 CIDR block to the VPC, add a route for ::/0 to the Internet Gateway, and allocate IPv6 addresses to the subnets.
Why this is correct
Standard procedure for public IPv6 access.
- ✗
Associate an IPv6 CIDR block, create an Egress-Only Internet Gateway, and route ::/0 to it.
Why it's wrong here
Egress-only does not allow inbound.
- ✗
Associate a /64 IPv6 CIDR block to the VPC, add a route for ::/0 to the Internet Gateway, and assign IPv6 addresses to instances.
Why it's wrong here
VPC IPv6 CIDR must be /56.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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