- A
Change the VPC CIDR to a non-overlapping range such as 172.16.0.0/16.
Why wrong: VPC CIDR cannot be changed after creation; you would need to recreate the VPC.
- B
Create a more specific route in the VPC route table for the on-premises network that is within the 10.0.0.0/8 range but not overlapping with the VPC's subnets.
More specific routes take precedence, so traffic to specific on-premises prefixes will go via VPN even if the VPC CIDR is a superset.
- C
Use a NAT gateway to translate the VPC's IP addresses to a different IP range when communicating with on-premises.
Why wrong: NAT is for outbound internet traffic, not for resolving IP overlap in VPN connections.
- D
Use AWS Transit Gateway with a network overlay to encapsulate traffic.
Why wrong: Transit Gateway does not provide IP overlay; it uses standard routing.
Quick Answer
The correct action is to create a more specific route in the VPC route table for the on-premises network that falls within the 10.0.0.0/8 range but does not overlap with the VPC’s own 10.0.0.0/16 subnets. This works because AWS route tables use the most specific matching route (longest prefix match) to determine traffic direction, so a route like 10.0.0.0/8 with a more specific destination, such as 10.1.0.0/16, will direct traffic to the VPN while the VPC’s internal 10.0.0.0/16 traffic stays local. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of CIDR overlap resolution and route prioritization, a common trap being that you cannot simply change the VPC CIDR or rely on NAT to fix routing conflicts. A key memory tip is “longest prefix wins”—when overlapping CIDRs exist, the more specific route always takes precedence, allowing you to carve out non-conflicting paths for hybrid connectivity.
ANS-C01 Network Implementation Practice Question
This ANS-C01 practice question tests your understanding of network implementation. 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 a 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. The company wants to ensure that traffic to on-premises from VPC does not overlap with VPC's own CIDR. Which action should be taken?
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 more specific route in the VPC route table for the on-premises network that is within the 10.0.0.0/8 range but not overlapping with the VPC's subnets.
Option A is correct because splitting the VPC into smaller subnets and using more specific routes can avoid overlap. Option B is wrong because NAT is used for internet access, not for route overlap. Option C is wrong because VPC CIDR cannot be changed without recreation. Option D is wrong because overlay network is not a standard solution for route overlap.
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.
- ✗
Change the VPC CIDR to a non-overlapping range such as 172.16.0.0/16.
Why it's wrong here
VPC CIDR cannot be changed after creation; you would need to recreate the VPC.
- ✓
Create a more specific route in the VPC route table for the on-premises network that is within the 10.0.0.0/8 range but not overlapping with the VPC's subnets.
- ✗
Use a NAT gateway to translate the VPC's IP addresses to a different IP range when communicating with on-premises.
- ✗
Use AWS Transit Gateway with a network overlay to encapsulate traffic.
Why it's wrong here
Transit Gateway does not provide IP overlay; it uses standard routing.
Common exam traps
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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 Implementation — study guide chapter
Learn the concepts, then practise the questions
- →
Network Implementation practice questions
Targeted practice on this topic area only
- →
All ANS-C01 questions
1,705 questions across all exam domains
- →
AWS Certified Advanced Networking Specialty ANS-C01 study guide
Full concept coverage aligned to exam objectives
- →
ANS-C01 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related ANS-C01 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Network Management and Operations practice questions
Practise ANS-C01 questions linked to Network Management and Operations.
Network Security, Compliance and Governance practice questions
Practise ANS-C01 questions linked to Network Security, Compliance and Governance.
Network Design practice questions
Practise ANS-C01 questions linked to Network Design.
Network Implementation practice questions
Practise ANS-C01 questions linked to Network Implementation.
ANS-C01 fundamentals practice questions
Practise ANS-C01 questions linked to ANS-C01 fundamentals.
ANS-C01 scenario practice questions
Practise ANS-C01 questions linked to ANS-C01 scenario.
ANS-C01 troubleshooting practice questions
Practise ANS-C01 questions linked to ANS-C01 troubleshooting.
Practice this exam
Start a free ANS-C01 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Create a more specific route in the VPC route table for the on-premises network that is within the 10.0.0.0/8 range but not overlapping with the VPC's subnets. — Option A is correct because splitting the VPC into smaller subnets and using more specific routes can avoid overlap. Option B is wrong because NAT is used for internet access, not for route overlap. Option C is wrong because VPC CIDR cannot be changed without recreation. Option D is wrong because overlay network is not a standard solution for route overlap.
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.
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
2 more ways this is tested on ANS-C01
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 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?
easy- A.Configure a VPN with overlapping CIDRs, it will still work
- B.Use NAT on the customer gateway to translate addresses
- ✓ C.Create a new VPC with a non-overlapping CIDR and migrate resources
- D.Use VPC peering to connect to on-premises
Why C: Overlapping CIDRs cause routing issues; the VPC CIDR must be changed to a non-overlapping range.
Variation 2. A company has a VPC with a CIDR of 10.0.0.0/16. They need to connect to a partner's VPC with CIDR 10.0.0.0/16 using a VPC peering connection. What is the issue with this configuration?
medium- A.The company has reached the maximum number of VPC peering connections
- B.VPC peering is only supported within the same region
- C.VPC peering does not support transitive routing
- ✓ D.Overlapping CIDR ranges are not supported for VPC peering
Why D: Option A is correct because VPC peering does not support overlapping CIDR blocks. Option B is wrong because VPC peering supports inter-region connections. Option C is wrong because there is no such limit on the number of peering connections. Option D is wrong because VPC peering does allow transitive routing via a middle VPC but overlapping CIDRs still cause issues.
Last reviewed: Jun 20, 2026
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.
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.