- A
The VPC route tables do not have route propagation enabled for the VGW. Enable route propagation in the route tables.
Why wrong: Even with propagation, static routes will override BGP routes.
- B
The BGP timers are set too high, causing slow convergence. Reduce the BGP keepalive and hold timers.
Why wrong: BGP timers affect convergence speed but are not the root cause of failover not happening at all.
- C
The VPC route tables have static routes that are overriding the BGP routes. Remove the static routes and rely on BGP routes propagated through the VGW.
Static routes have higher priority than BGP routes, preventing failover.
- D
The BGP configuration on the on-premises router is using AS_PATH prepending, making the backup path less preferred. Remove AS_PATH prepending.
Why wrong: AS_PATH prepending is used for path selection, but static routes are overriding BGP.
Quick Answer
The answer is that static routes in the VPC route tables override BGP-propagated routes, causing the failover to fail. This happens because AWS VPC route tables assign a higher priority to static routes than to dynamic BGP routes, regardless of the BGP session’s health. Even when a Direct Connect connection fails and its BGP session drops, the static route remains in the table, forcing traffic toward the failed virtual private gateway instead of allowing BGP to dynamically switch to the active path. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of route priority and the interaction between static and BGP routes in hybrid networking designs. A common trap is assuming BGP will automatically override static entries, but AWS’s routing logic is the opposite. To resolve the BGP route priority static routes conflict, remove the static routes and enable route propagation on the VGW. Memory tip: think of static routes as “stubborn” — they stay put even when the path breaks, so let BGP do the dynamic failover work.
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 large financial services company is migrating its on-premises data center to AWS. The network design must meet strict low-latency requirements for trading applications that communicate with external exchanges. The company has two AWS Direct Connect connections from two different providers to two different AWS Direct Connect locations in the same region. They have a VPC with multiple subnets across three Availability Zones. The trading applications are deployed on EC2 instances in private subnets and need to communicate with external exchanges over the Direct Connect connections. The company also requires high availability and automatic failover if one Direct Connect connection fails. The network team has configured two virtual interfaces (VIFs) for private connectivity to the VPC, one on each Direct Connect connection, and has set up BGP sessions. However, during a failover test, traffic does not fail over as expected. The team notices that the VPC route tables have static routes pointing to the virtual private gateway (VGW) with the same prefix, but no BGP routes are propagated. What is the most likely cause of the failover issue, and what should be done to resolve it?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 VPC route tables have static routes that are overriding the BGP routes. Remove the static routes and rely on BGP routes propagated through the VGW.
The failover issue occurs because static routes in the VPC route tables take precedence over BGP-propagated routes, even when the BGP session goes down. Since the static routes point to the virtual private gateway (VGW) with the same prefix, traffic continues to use the failed Direct Connect connection instead of failing over to the active one. Removing the static routes and enabling route propagation allows BGP to dynamically update the route tables based on the availability of the Direct Connect connections.
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 route tables do not have route propagation enabled for the VGW. Enable route propagation in the route tables.
Why it's wrong here
Even with propagation, static routes will override BGP routes.
- ✗
The BGP timers are set too high, causing slow convergence. Reduce the BGP keepalive and hold timers.
Why it's wrong here
BGP timers affect convergence speed but are not the root cause of failover not happening at all.
- ✓
The VPC route tables have static routes that are overriding the BGP routes. Remove the static routes and rely on BGP routes propagated through the VGW.
Why this is correct
Static routes have higher priority than BGP routes, preventing failover.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The BGP configuration on the on-premises router is using AS_PATH prepending, making the backup path less preferred. Remove AS_PATH prepending.
Why it's wrong here
AS_PATH prepending is used for path selection, but static routes are overriding BGP.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the misconception that enabling route propagation alone ensures failover, but the trap here is that static routes in the VPC route table take precedence over BGP-propagated routes, so they must be removed for automatic failover to work.
Detailed technical explanation
How to think about this question
In AWS, VPC route tables support both static routes and propagated routes from a virtual private gateway. Static routes have a higher priority (lower administrative distance) than BGP-propagated routes, meaning they are always preferred regardless of the BGP session state. When a Direct Connect connection fails, the BGP session drops, and the propagated routes are withdrawn, but the static route remains, causing traffic to blackhole. This behavior is consistent with RFC 4271 and AWS documentation, which state that static routes override dynamic routes in the same route table.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
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: The VPC route tables have static routes that are overriding the BGP routes. Remove the static routes and rely on BGP routes propagated through the VGW. — The failover issue occurs because static routes in the VPC route tables take precedence over BGP-propagated routes, even when the BGP session goes down. Since the static routes point to the virtual private gateway (VGW) with the same prefix, traffic continues to use the failed Direct Connect connection instead of failing over to the active one. Removing the static routes and enabling route propagation allows BGP to dynamically update the route tables based on the availability of the Direct Connect connections.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 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.
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