The answer is to associate an IPv6 CIDR block with the VPC, enable IPv6 on the subnet, and add a route for ::/0 to an egress-only internet gateway or internet gateway. These three steps are necessary because IPv6 operates differently from IPv4: you must explicitly assign an IPv6 block to the VPC, then configure the subnet to support IPv6 addressing and auto-assign IPv6 addresses to instances, and finally direct outbound traffic via a route that leverages an egress-only IGW (for outbound-only communication) or a standard IGW for bidirectional traffic. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of IPv6 VPC configuration steps and the critical distinction that IPv6 does not use NAT or NAT gateways—a common trap where candidates mistakenly select NAT options. Remember the memory tip: “No NAT for IPv6; egress-only is the trick.”
ANS-C01 Network Management and Operations Practice Question
This ANS-C01 practice question tests your understanding of network management and operations. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 of 10.0.0.0/16. The network engineer needs to add an IPv6 CIDR block to the VPC and ensure that EC2 instances can communicate over IPv6. Which THREE steps are necessary to achieve this?
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 route table for ::/0 to an egress-only internet gateway.
Options A, B, and D are correct. A: Associate an IPv6 CIDR block. B: Enable IPv6 on the subnet. D: Add a route for ::/0 to an egress-only internet gateway or internet gateway. Option C is wrong because IPv6 traffic uses egress-only IGW, not NAT. Option E is wrong because security groups do not need to be updated specifically for IPv6; they work for both.
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
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Update security group rules to allow IPv6 traffic.
Why it's wrong here
Security groups support both IPv4 and IPv6; no special update required.
✓
Add a route in the subnet route table for ::/0 to an egress-only internet gateway.
Common exam trap: usable hosts are not the same as total addresses
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
How to think about this question
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.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
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
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
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.
Network Management and Operations — This question tests Network Management and Operations — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Add a route in the subnet route table for ::/0 to an egress-only internet gateway. — Options A, B, and D are correct. A: Associate an IPv6 CIDR block. B: Enable IPv6 on the subnet. D: Add a route for ::/0 to an egress-only internet gateway or internet gateway. Option C is wrong because IPv6 traffic uses egress-only IGW, not NAT. Option E is wrong because security groups do not need to be updated specifically for IPv6; they work for both.
What should I do if I get this ANS-C01 question wrong?
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.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.