- A
The VPC will automatically reassign a new CIDR to avoid the conflict.
Why wrong: AWS does not automatically modify VPC CIDRs.
- B
The BGP session will fail to establish due to the prefix conflict.
Why wrong: BGP session establishment is not affected by prefix overlap; only route advertisement is rejected.
- C
The BGP session will be established, but the overlapping prefix will be ignored and not programmed into the VPC route tables.
AWS does not allow overlapping prefixes to be injected into VPC route tables to prevent routing conflicts.
- D
The on-premises prefix will take precedence and override the VPC route.
Why wrong: AWS prioritizes local VPC routes over learned routes, so the VPC CIDR remains.
Question 1,157 of 1,705
Handling Overlapping BGP Prefixes with VPC CIDR in Direct Connect
This ANS-C01 practice question tests your understanding of network implementation. 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 network engineer is setting up a Direct Connect connection from an on-premises data center to AWS. The connection uses a private VIF to connect to a VPC via a Direct Connect gateway. The on-premises network is advertising a BGP prefix 10.0.0.0/16, which overlaps with the VPC CIDR 10.0.0.0/16. What is the expected behavior?
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
✓
The BGP session will be established, but the overlapping prefix will be ignored and not programmed into the VPC route tables.
When a BGP prefix advertised over a Direct Connect private VIF overlaps with the VPC CIDR, the BGP session establishes successfully, but AWS ignores the overlapping prefix and does not install it into the VPC route tables. This is because AWS always prefers the local VPC route over any propagated BGP route for the same prefix, preventing traffic destined for the VPC from being blackholed or misrouted to on-premises.
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.
- ✗
The VPC will automatically reassign a new CIDR to avoid the conflict.
Why it's wrong here
AWS does not automatically modify VPC CIDRs.
- ✗
The BGP session will fail to establish due to the prefix conflict.
Why it's wrong here
BGP session establishment is not affected by prefix overlap; only route advertisement is rejected.
- ✓
The BGP session will be established, but the overlapping prefix will be ignored and not programmed into the VPC route tables.
Why this is correct
AWS does not allow overlapping prefixes to be injected into VPC route tables to prevent routing conflicts.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The on-premises prefix will take precedence and override the VPC route.
Why it's wrong here
AWS prioritizes local VPC routes over learned routes, so the VPC CIDR remains.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume BGP session failure due to prefix overlap, but BGP itself has no mechanism to reject a session based on prefix overlap; the overlap only affects route installation, not session state.
Detailed technical explanation
How to think about this question
Under the hood, the Direct Connect gateway and virtual private gateway use BGP best-path selection, but AWS applies a local preference that favors directly attached VPC routes over learned BGP routes for identical prefixes. In a real-world scenario, if you need to advertise a more specific prefix (e.g., 10.0.1.0/24) from on-premises to override the VPC default, you must ensure the on-premises prefix is more specific than the VPC CIDR and that the VPC route tables do not already have a more specific local route.
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
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 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 — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The BGP session will be established, but the overlapping prefix will be ignored and not programmed into the VPC route tables. — When a BGP prefix advertised over a Direct Connect private VIF overlaps with the VPC CIDR, the BGP session establishes successfully, but AWS ignores the overlapping prefix and does not install it into the VPC route tables. This is because AWS always prefers the local VPC route over any propagated BGP route for the same prefix, preventing traffic destined for the VPC from being blackholed or misrouted to on-premises.
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.
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 →
Keep practising
More ANS-C01 practice questions
- A financial services company has a VPC with a public subnet and a private subnet. EC2 instances in the private subnet ne…
- A company is designing a network security architecture for a multi-account environment using AWS Transit Gateway. The se…
- A company is using AWS Direct Connect to connect its on-premises network to AWS. The company wants to encrypt all traffi…
- A company uses AWS Transit Gateway to connect multiple VPCs and on-premises networks via AWS Site-to-Site VPN. The secur…
- A company runs a web application on EC2 instances behind an Application Load Balancer (ALB). The application must be acc…
- A global e-commerce company uses a hub-and-spoke network topology with a transit VPC in us-east-1. Each spoke VPC has an…
Last reviewed: Jul 4, 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.