This ANS-C01 practice question tests your understanding of network design. 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 block of 10.0.0.0/16. It needs to connect to an on-premises data center via AWS Direct Connect. The on-premises network uses 10.0.0.0/8. Which action should the network engineer take to avoid IP address overlap?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a new VPC with a non-overlapping CIDR block, such as 172.16.0.0/16, and migrate resources.
To avoid overlapping IP ranges, the VPC CIDR must not overlap with the on-premises network. The on-premises uses 10.0.0.0/8, which includes 10.0.0.0/16. The company must change the VPC CIDR to a non-overlapping range, such as 172.16.0.0/16 (RFC 1918 private range). Option B is incorrect because NAT does not solve overlap for VPN/Direct Connect routes. Option C is incorrect because adding a secondary CIDR does not remove the overlap. Option D is incorrect because Direct Connect does not support overlapping IPs.
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.
✗
Use a NAT gateway to translate the VPC addresses when connecting to on-premises.
Why it's wrong here
NAT does not resolve routing conflicts; the routes would still overlap.
✗
Use AWS Direct Connect gateway to automatically handle overlapping IPs.
Why it's wrong here
Direct Connect gateway does not resolve IP overlaps.
✗
Add a secondary CIDR block to the VPC and use it for resources that need to connect to on-premises.
Why it's wrong here
Secondary CIDR also must not overlap; the primary still overlaps.
✓
Create a new VPC with a non-overlapping CIDR block, such as 172.16.0.0/16, and migrate resources.
Why this is correct
Changing the VPC CIDR to a non-overlapping range solves the conflict.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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 Design — This question tests Network Design — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Create a new VPC with a non-overlapping CIDR block, such as 172.16.0.0/16, and migrate resources. — To avoid overlapping IP ranges, the VPC CIDR must not overlap with the on-premises network. The on-premises uses 10.0.0.0/8, which includes 10.0.0.0/16. The company must change the VPC CIDR to a non-overlapping range, such as 172.16.0.0/16 (RFC 1918 private range). Option B is incorrect because NAT does not solve overlap for VPN/Direct Connect routes. Option C is incorrect because adding a secondary CIDR does not remove the overlap. Option D is incorrect because Direct Connect does not support overlapping IPs.
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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