ANS-C01 Network Implementation Practice Question
A company is deploying a VPC with IPv6 support. The VPC has a CIDR block of 10.0.0.0/16 and an assigned IPv6 CIDR block of 2600:1f16:xxxx:xxxx::/56. The company wants EC2 instances in a public subnet to be able to communicate with the internet using IPv6. Which configuration is necessary?
⚠ Common exam trap
Watch out — candidates often confuse the egress-only internet gateway with a NAT gateway or assume that an internet gateway alone suffices for IPv6, forgetting that the internet gateway supports both inbound and outbound traffic, whereas the EIGW is specifically required for outbound-only IPv6 communication to prevent inbound connections.
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
✓
Attach an egress-only internet gateway to the VPC and add a route for ::/0 to the egress-only internet gateway in the public subnet route table.
An egress-only internet gateway (EIGW) is the AWS-managed service designed to enable outbound-only IPv6 communication from a VPC to the internet. Since IPv6 addresses are globally unique and publicly routable, a NAT gateway (used for IPv4) is not needed; instead, the EIGW allows instances to initiate outbound traffic while preventing any unsolicited inbound connections. Adding a route for ::/0 to the EIGW in the public subnet route table directs all outbound IPv6 traffic through it.
Answer analysis
Option-by-option breakdown
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 add a route for ::/0 to the NAT gateway in the public subnet route table.
Why it's wrong here
NAT gateways support IPv4 only.
- ✗
Attach an internet gateway to the VPC and add a route for 0.0.0.0/0 to the internet gateway in the public subnet route table.
Why it's wrong here
That is for IPv4, not IPv6.
- ✗
Set up a NAT64 translation service to convert IPv6 requests to IPv4.
Why it's wrong here
Unnecessary for simple outbound-only IPv6 access.
- ✓
Attach an egress-only internet gateway to the VPC and add a route for ::/0 to the egress-only internet gateway in the public subnet route table.
Why this is correct
Provides outbound-only IPv6 internet access.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This ANS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the ANS-C01 exam.