- A
Establish a VPC peering connection between the VPC and on-premises network.
Why wrong: VPC peering does not support overlapping CIDRs.
- B
Use AWS Direct Connect with a private VIF and static routes to route traffic.
Why wrong: Direct Connect cannot resolve IP overlap; routes will conflict.
- C
Create a new VPC with a non-overlapping CIDR, connect both VPCs via Transit Gateway, and use NAT on the Transit Gateway attachment to the on-premises network.
Transit Gateway with NAT attachment allows IP translation to resolve overlap.
- D
Deploy a NAT instance in the VPC to translate on-premises IPs.
Why wrong: A single NAT instance is a bottleneck and does not scale for all traffic.
Question 264 of 1,705
ANS-C01 Network Design Practice Question
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 of 10.0.0.0/16 and needs to connect to an on-premises network via AWS Direct Connect. The on-premises network uses 10.0.0.0/16. Which solution allows connectivity without IP overlap?
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
✓
Create a new VPC with a non-overlapping CIDR, connect both VPCs via Transit Gateway, and use NAT on the Transit Gateway attachment to the on-premises network.
Option C is correct because when both the VPC and on-premises network use the same 10.0.0.0/16 CIDR, direct connectivity is impossible due to overlapping IP ranges. By creating a new VPC with a non-overlapping CIDR, connecting both VPCs via Transit Gateway, and applying NAT on the Transit Gateway attachment to the on-premises network, traffic from the original VPC can be source-NATed to the new VPC's range before being forwarded to on-premises, resolving the overlap. This allows the on-premises network to receive traffic with unique IPs, avoiding routing conflicts.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Establish a VPC peering connection between the VPC and on-premises network.
Why it's wrong here
VPC peering does not support overlapping CIDRs.
- ✗
Use AWS Direct Connect with a private VIF and static routes to route traffic.
Why it's wrong here
Direct Connect cannot resolve IP overlap; routes will conflict.
- ✓
Create a new VPC with a non-overlapping CIDR, connect both VPCs via Transit Gateway, and use NAT on the Transit Gateway attachment to the on-premises network.
- ✗
Deploy a NAT instance in the VPC to translate on-premises IPs.
Why it's wrong here
A single NAT instance is a bottleneck and does not scale for all traffic.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The ANS-C01 exam often tests the misconception that Direct Connect alone can handle overlapping IPs by using static routes or BGP communities, but without NAT or address translation, overlapping CIDRs cause asymmetric routing and unreachability.
Detailed technical explanation
How to think about this question
Transit Gateway supports Network Address Translation (NAT) on attachments via AWS Transit Gateway Connect or by using a NAT appliance in a shared services VPC. In this scenario, the NAT function translates the source IP of packets from the original VPC (10.0.0.0/16) to a unique IP in the new VPC's CIDR (e.g., 172.16.0.0/16) before sending them to on-premises. This ensures that on-premises routes see non-overlapping addresses, and return traffic is correctly forwarded back through the Transit Gateway, where reverse NAT restores the original source IP. This approach is commonly used in mergers or migrations where overlapping CIDRs must coexist.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a new VPC with a non-overlapping CIDR, connect both VPCs via Transit Gateway, and use NAT on the Transit Gateway attachment to the on-premises network. — Option C is correct because when both the VPC and on-premises network use the same 10.0.0.0/16 CIDR, direct connectivity is impossible due to overlapping IP ranges. By creating a new VPC with a non-overlapping CIDR, connecting both VPCs via Transit Gateway, and applying NAT on the Transit Gateway attachment to the on-premises network, traffic from the original VPC can be source-NATed to the new VPC's range before being forwarded to on-premises, resolving the overlap. This allows the on-premises network to receive traffic with unique IPs, avoiding routing conflicts.
What should I do if I get this ANS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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