- A
Update security group rules to allow IPv6 traffic.
Why wrong: Security groups support both IPv4 and IPv6; no special update required.
- B
Add a route in the subnet route table for ::/0 to an egress-only internet gateway.
Egress-only IGW allows outbound IPv6 traffic.
- C
Configure a NAT64 gateway for IPv6 to IPv4 translation.
Why wrong: NAT64 is not needed; egress-only IGW is used for outbound IPv6.
- D
Associate an Amazon-provided IPv6 CIDR block with the VPC.
IPv6 CIDR block must be associated with the VPC.
- E
Assign IPv6 addresses to the subnets and enable auto-assign IPv6 address.
Subnets need IPv6 CIDR and auto-assign setting.
Question 873 of 1,705
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 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 route table for ::/0 to an egress-only internet gateway.
To enable IPv6 in a VPC, three steps are necessary: associate an Amazon-provided IPv6 CIDR block with the VPC (D), add a route in the subnet route table for ::/0 to an egress-only internet gateway (B), and assign IPv6 addresses to the subnets while enabling auto-assign IPv6 address (E). Option A is incorrect because security group rules do need to be updated to allow IPv6 traffic, but the question asks which three steps are necessary, and updating security groups is not listed as one of the correct options. Option C is incorrect because a NAT64 gateway is used for IPv6-to-IPv4 translation, not for providing IPv6 connectivity.
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.
Why this is correct
Egress-only IGW allows outbound IPv6 traffic.
Related concept
CIDR notation defines the prefix length.
- ✗
Configure a NAT64 gateway for IPv6 to IPv4 translation.
Why it's wrong here
NAT64 is not needed; egress-only IGW is used for outbound IPv6.
- ✓
Associate an Amazon-provided IPv6 CIDR block with the VPC.
- ✓
Assign IPv6 addresses to the subnets and enable auto-assign IPv6 address.
Common exam traps
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.
Visual reference
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.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
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. — To enable IPv6 in a VPC, three steps are necessary: associate an Amazon-provided IPv6 CIDR block with the VPC (D), add a route in the subnet route table for ::/0 to an egress-only internet gateway (B), and assign IPv6 addresses to the subnets while enabling auto-assign IPv6 address (E). Option A is incorrect because security group rules do need to be updated to allow IPv6 traffic, but the question asks which three steps are necessary, and updating security groups is not listed as one of the correct options. Option C is incorrect because a NAT64 gateway is used for IPv6-to-IPv4 translation, not for providing IPv6 connectivity.
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.
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Last reviewed: Jun 20, 2026
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