ANS-C01 Network Implementation Practice Question
A company has a VPC with an IPv4 CIDR of 10.0.0.0/16 and needs to connect to an on-premises network using AWS Site-to-Site VPN. The on-premises network uses 10.0.0.0/8. What should be done to avoid overlapping CIDRs?
⚠ Common exam trap
The ANS-C01 exam often tests the misconception that NAT on the customer gateway can solve overlapping CIDR issues in Site-to-Site VPN, but candidates must understand that NAT does not resolve the underlying routing conflict because the VPC still sees the overlapping range as local.
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 and migrate resources
AWS Site-to-Site VPN requires non-overlapping IP CIDRs between the VPC and the on-premises network for proper routing. The VPC uses 10.0.0.0/16, which falls entirely within the on-premises 10.0.0.0/8, causing a conflict that prevents the VPN from establishing routes correctly. Creating a new VPC with a non-overlapping CIDR (e.g., 172.16.0.0/16) and migrating resources resolves the overlap, enabling the VPN connection.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure a VPN with overlapping CIDRs, it will still work
Why it's wrong here
Overlapping CIDRs cause routing conflicts.
- ✗
Use NAT on the customer gateway to translate addresses
Why it's wrong here
NAT can help but adds complexity; it's better to avoid overlap.
- ✓
Create a new VPC with a non-overlapping CIDR and migrate resources
Why this is correct
Changing the VPC CIDR requires recreation; a new VPC is the practical solution.
- ✗
Use VPC peering to connect to on-premises
Why it's wrong here
VPC peering does not solve overlapping CIDRs.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.