The answer is to prepend the AS path on the VPN connection to make it less preferred. This works because BGP selects the route with the shortest AS path length by default, so by artificially lengthening the AS path on the VPN, the Direct Connect route remains the primary path for traffic from on-premises to AWS. When Direct Connect fails, the VPN route becomes the only available path, triggering automatic failover. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of BGP path selection and how to manipulate routing preferences without changing the underlying network topology. A common trap is assuming you need to adjust local preference or MED, but AS path prepending is the cleanest method for outbound traffic control from on-premises. Remember the memory tip: “Longer path, lesser path” — the longer the AS path, the less preferred the route.
ANS-C01 Network Design Practice Question
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 is designing a hybrid network using AWS Direct Connect and AWS Site-to-Site VPN as backup. They want to ensure that traffic from on-premises to AWS uses Direct Connect when available and fails over to VPN automatically. Which BGP configuration should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Prepend AS path on the VPN connection to make it less preferred.
Option B is correct because prepending the AS path on the VPN connection increases the AS path length, making the VPN route less preferred compared to the Direct Connect route. BGP selects the path with the shortest AS path length by default, so the Direct Connect path will be chosen as the primary path. When Direct Connect fails, the VPN route becomes the only available path and traffic automatically fails over.
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.
✗
Set a higher BGP local preference on the VPN connection.
Why it's wrong here
Higher local preference is more preferred, which would prefer VPN over Direct Connect.
✓
Prepend AS path on the VPN connection to make it less preferred.
Why this is correct
Longer AS path is less preferred, so Direct Connect will be chosen.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use the same BGP attributes for both connections and let ECMP handle load balancing.
Why it's wrong here
ECMP would load share, not provide active/backup.
✗
Set a higher Multi-Exit Discriminator (MED) on the Direct Connect connection.
Why it's wrong here
Higher MED is less preferred, which would make Direct Connect less preferred.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the misconception that MED is used to influence inbound traffic preference from a single AS, but here the trap is that candidates confuse MED (which is compared only for paths from the same neighboring AS) with AS path prepending, which works across different AS paths and is the correct method for this failover design.
Detailed technical explanation
How to think about this question
AS path prepending works by adding repeated copies of the local AS number to the BGP AS_PATH attribute, artificially inflating the path length. BGP's path selection algorithm compares AS path length before MED or local preference (after weight and local preference), making prepending a reliable method to deprioritize a backup path. In a real-world scenario, you might prepend multiple times (e.g., 'set as-path prepend 3') to ensure the VPN path is never selected unless Direct Connect is completely down.
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: Prepend AS path on the VPN connection to make it less preferred. — Option B is correct because prepending the AS path on the VPN connection increases the AS path length, making the VPN route less preferred compared to the Direct Connect route. BGP selects the path with the shortest AS path length by default, so the Direct Connect path will be chosen as the primary path. When Direct Connect fails, the VPN route becomes the only available path and traffic automatically fails over.
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 →
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 is designing a hybrid network with AWS Direct Connect and AWS Site-to-Site VPN as backup. The primary Direct Connect connection uses a private VIF to a VPC. If the Direct Connect fails, traffic should automatically fail over to the VPN connection. What is the MOST reliable way to achieve this failover?
medium
A.Use BGP on Direct Connect and static routes on the VPN connection, with a higher metric for the VPN static route.
B.Configure static routes on the customer gateway device with a lower metric for the Direct Connect interface.
✓ C.Use BGP on both connections and prepend AS paths on the Direct Connect routes to make them less preferred.
D.Use BGP on both connections and set a lower local preference on the Direct Connect routes.
Why C: Option C is correct because using BGP on both connections allows you to influence route selection via AS path prepending. By prepending the AS path on the Direct Connect routes, you make them appear less preferred compared to the VPN routes, ensuring that under normal conditions traffic uses Direct Connect. When Direct Connect fails, the BGP session drops, the routes are withdrawn, and traffic automatically fails over to the VPN without any manual intervention or reliance on static metrics.
Last reviewed: Jun 30, 2026
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.
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.