Question 369 of 247
Overlapping CIDR: NAT Instance Solution
A company has a VPC with a CIDR block of 10.0.0.0/16. They need to connect to an on-premises network using a site-to-site VPN. The on-premises network uses 10.0.0.0/16 as well. Which solution avoids routing conflicts?
Quick Answer
The correct solution is to use a NAT instance to translate addresses for overlapping CIDR ranges. When a VPC and an on-premises network both use 10.0.0.0/16, a site-to-site VPN would create routing conflicts because the same IP space exists on both sides. A NAT instance resolves this by performing destination NAT (DNAT) on inbound traffic from on-premises, translating it into a non-conflicting IP range inside the VPC, and source NAT (SNAT) on outbound traffic back, effectively hiding the overlap from the routing tables. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of hybrid networking workarounds when renumbering is not an option—a common trap is assuming VPC peering or a simple VPN will suffice, but overlapping CIDR blocks require address translation. Remember the memory tip: “Same CIDR? NAT the traffic.”
⚠ Common exam trap
Many candidates assume a second VPN connection or VPC peering can solve overlapping CIDR issues, but AWS requires unique, non-overlapping IP ranges for both VPN route propagation and VPC peering, making NAT the only viable option among the choices.
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
✓
Use a NAT instance to translate addresses for overlapping ranges.
A NAT instance can translate the overlapping IP addresses from the on-premises network (10.0.0.0/16) to a different IP range within the VPC, allowing communication without routing conflicts. The NAT instance performs destination NAT (DNAT) for inbound traffic and source NAT (SNAT) for outbound traffic, effectively hiding the overlap. This is a common workaround when both networks use the same CIDR block and cannot be renumbered.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Attach an Internet Gateway and use public IPs for communication.
Why it's wrong here
Internet Gateway doesn't resolve overlap; security concerns.
- ✗
Set up a second VPN connection to a different virtual private gateway.
Why it's wrong here
Multiple VPNs don't solve IP overlap.
- ✗
Create a VPC peering connection between the VPC and on-premises network.
Why it's wrong here
Peering requires non-overlapping CIDRs.
- ✓
Use a NAT instance to translate addresses for overlapping ranges.
Why this is correct
NAT can translate overlapping IPs.
Visual reference
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more way this is tested on SOA-C02
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company has a VPC with an IPv4 CIDR block of 10.0.0.0/16. They need to connect to an on-premises network with a CIDR of 10.0.0.0/8. What is the issue?
easy- A.The on-premises CIDR is private and cannot be used with AWS.
- B.AWS does not support /8 CIDR blocks.
- ✓ C.The CIDR blocks overlap, causing routing conflicts.
- D.The VPC CIDR is too large.
Why C: Overlapping CIDR blocks prevent VPC peering or VPN connections because routes conflict. Option A is not the issue. Option B is not the primary issue. Option D is not directly a problem.
Last reviewed: Jun 24, 2026
This SOA-C02 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 SOA-C02 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.