ANS-C01 IPv6 route to internet gateway 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 internet-facing Application Load Balancer. The VPC is already associated with an IPv6 CIDR block. What additional configuration is required? (Choose two.)
⚠ Common exam trap
A common trap is thinking that you need to assign an IPv6 address directly to the ALB's network interface, but the ALB inherits IPv6 support from the subnet's IPv6 CIDR.
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
✓
Add a route in the subnet's route table for ::/0 to the Internet Gateway.
Options B and C are correct. To support IPv6 clients on an internet-facing ALB, the subnet where the ALB is deployed must have an IPv6 CIDR block associated (C), and the subnet's route table must include a route for ::/0 to the internet gateway (B). Option A is incorrect because NAT64/DNS64 is not needed; the ALB natively supports IPv6. Option D is incorrect because the ALB uses the subnet's IPv6 CIDR, not an assigned IPv6 address on its network interface. Option E is incorrect because an Egress-Only Internet Gateway is used for outbound-only IPv6 traffic from private subnets, not for internet-facing ALBs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure NAT64 and DNS64 on the VPC.
Why it's wrong here
Incorrect. NAT64 and DNS64 are used for translating IPv6 traffic to IPv4 for resources that only have IPv4, but an internet-facing ALB supports IPv6 natively and does not require translation.
- ✓
Add a route in the subnet's route table for ::/0 to the Internet Gateway.
Why this is correct
Correct. The route ::/0 to the internet gateway is required to allow IPv6 traffic to and from the internet for the subnet where the ALB resides.
- ✓
Associate an IPv6 CIDR block with the public subnet where the ALB is deployed.
Why this is correct
Correct. The public subnet must have an IPv6 CIDR block associated so that the ALB can use IPv6 addresses from that subnet.
- ✗
Assign an IPv6 address to the ALB's network interface.
Why it's wrong here
Incorrect. The ALB does not need an IPv6 address assigned to its network interface; it uses the subnet's IPv6 CIDR to serve IPv6 clients.
- ✗
Create an Egress-Only Internet Gateway for the VPC.
Why it's wrong here
Incorrect. An Egress-Only Internet Gateway is for outbound-only IPv6 traffic from private subnets, not for an internet-facing ALB which requires inbound IPv6 traffic.
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JA
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.