The correct answer is that the on-premises default route advertisement causes a routing conflict. When the on-premises router advertises 0.0.0.0/0 via BGP over the private VIF, the VPC route table now contains two default routes: one pointing to the internet gateway and one learned via BGP. Since BGP-learned routes are more specific than static or propagated routes in AWS, traffic from on-premises destined for the internet enters the VPC and matches the BGP default route, which forwards it back toward the on-premises router or black-holes it, creating a routing loop instead of sending it to the internet gateway. On the ANS-C01 exam, this scenario tests your understanding of BGP route propagation and route table priority in hybrid networking, often appearing as a trap where candidates assume the internet gateway will always win. Remember the memory tip: “BGP beats the gateway” — a BGP-advertised default will override a static default route to the internet gateway, so always filter or deny default route advertisements from on-premises over a private VIF.
ANS-C01 Network Management and Operations Practice Question
This ANS-C01 practice question tests your understanding of network management and operations. 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 Direct Connect connection with a private VIF to a VPC. The on-premises router is advertising a default route (0.0.0.0/0) via BGP. The VPC has an internet gateway attached, and the route table has a default route to the internet gateway. The network team notices that traffic from on-premises to the internet is not working as expected. What is the most likely cause?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The on-premises router is advertising a default route, causing a routing conflict.
The on-premises router advertising a default route (0.0.0.0/0) via BGP over the private VIF causes a routing conflict because the VPC route table already has a default route pointing to the internet gateway. When traffic from on-premises destined for the internet enters the VPC, it matches the more specific BGP-learned default route and is forwarded back toward the on-premises router (or black-holed), rather than being sent to the internet gateway. This creates a routing loop or asymmetric routing, breaking internet connectivity from 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 on-premises router is advertising a default route, causing a routing conflict.
Why this is correct
The default route from Direct Connect may override the internet gateway route, breaking internet access for on-premises traffic.
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 VPC route table does not have a route to the internet gateway for the on-premises traffic.
Why it's wrong here
The default route to internet gateway exists but may not be used due to route preference.
✗
The private VIF is associated with the wrong VLAN.
Why it's wrong here
VLAN association would prevent connectivity entirely.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the misconception that a default route advertised via BGP over Direct Connect is harmless or that the internet gateway route will always take precedence, but in reality, the VPC route table matches the most specific route (both are /0), and the BGP-learned route over the virtual private gateway is preferred for traffic entering the VPC from on-premises, causing the conflict.
Detailed technical explanation
How to think about this question
In AWS Direct Connect, a private VIF allows BGP to exchange routes between on-premises and the VPC. When the on-premises router advertises 0.0.0.0/0, the VPC route table installs it as a static route (via the virtual private gateway), which has a higher precedence than the local default route to the internet gateway for traffic originating from on-premises (since the VPC uses the most specific matching route). This can lead to traffic being sent back to on-premises, creating a routing loop. A common real-world scenario is when an organization intends to use Direct Connect only for private IP traffic but inadvertently advertises a default route, breaking internet-bound traffic.
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 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Management and Operations — This question tests Network Management and Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The on-premises router is advertising a default route, causing a routing conflict. — The on-premises router advertising a default route (0.0.0.0/0) via BGP over the private VIF causes a routing conflict because the VPC route table already has a default route pointing to the internet gateway. When traffic from on-premises destined for the internet enters the VPC, it matches the more specific BGP-learned default route and is forwarded back toward the on-premises router (or black-holed), rather than being sent to the internet gateway. This creates a routing loop or asymmetric routing, breaking internet connectivity from 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.
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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Question Discussion
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