This ANS-C01 practice question tests your understanding of network design. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 CIDR 10.0.0.0/16 and needs to connect to an on-premises network with CIDR 10.0.0.0/8. They plan to use AWS Direct Connect with a private virtual interface. What should they do to resolve the overlapping CIDR conflict?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change the VPC CIDR to a non-overlapping range, such as 172.16.0.0/16, and re-create the VPC with the new CIDR.
Option C is correct because AWS does not support network address translation (NAT) for overlapping CIDRs on a Direct Connect private virtual interface. The only way to resolve the conflict is to change the VPC CIDR to a non-overlapping range (e.g., 172.16.0.0/16) and recreate the VPC, as the VPC CIDR cannot be modified after creation. This ensures that routes between the VPC and on-premises network do not conflict.
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.
✗
Create a VPN connection with dynamic routing and use BGP to advertise the VPC CIDR.
Why it's wrong here
BGP does not resolve overlapping CIDRs; routes with overlapping prefixes cause conflicts.
✗
Create a VPC peering connection between the VPC and the on-premises network.
Why it's wrong here
VPC peering does not support overlapping CIDR ranges.
✓
Change the VPC CIDR to a non-overlapping range, such as 172.16.0.0/16, and re-create the VPC with the new CIDR.
Why this is correct
The only solution is to use non-overlapping IP address ranges.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use a NAT Gateway in the VPC to translate the on-premises IP addresses.
Why it's wrong here
NATGateway translates private IPs from the VPC to the internet, not for overlapping CIDRs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume NAT or VPN can magically resolve overlapping IP ranges, but AWS Direct Connect private VIFs require non-overlapping CIDRs for proper routing, and no AWS service (including NAT Gateway or VPN) can translate on-premises IPs in this context.
Detailed technical explanation
How to think about this question
When using Direct Connect with a private virtual interface, the VPC and on-premises networks exchange routes via BGP over the VIF. If CIDRs overlap, the AWS side will reject the more specific or conflicting route advertisement, or traffic will be unpredictably routed. In real-world scenarios, overlapping CIDRs often require renumbering one side; AWS allows you to add secondary CIDRs to a VPC but not change the primary, so creating a new VPC with a non-overlapping range is the standard solution.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: Change the VPC CIDR to a non-overlapping range, such as 172.16.0.0/16, and re-create the VPC with the new CIDR. — Option C is correct because AWS does not support network address translation (NAT) for overlapping CIDRs on a Direct Connect private virtual interface. The only way to resolve the conflict is to change the VPC CIDR to a non-overlapping range (e.g., 172.16.0.0/16) and recreate the VPC, as the VPC CIDR cannot be modified after creation. This ensures that routes between the VPC and on-premises network do not conflict.
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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Question Discussion
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