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 is setting up a Direct Connect connection to connect its on-premises data center to AWS. The connection is established, and a private virtual interface (VIF) is configured. The on-premises router can ping the VIF's Amazon side IP address, but cannot ping an EC2 instance in the VPC. The VPC has a virtual private gateway attached, and the route tables are correctly configured. What should the company check next?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Verify that the on-premises router is advertising the VPC CIDR to the Direct Connect router.
The on-premises router can ping the VIF's Amazon side IP, confirming that Layer 2 and Layer 3 connectivity over the Direct Connect link is working, and BGP is established. However, the inability to ping the EC2 instance indicates that return traffic from the VPC is not reaching the on-premises network. For return traffic to be routed correctly, the on-premises router must advertise the VPC CIDR (or a specific prefix) to the Direct Connect router via BGP; otherwise, the AWS side will not forward traffic destined for the on-premises network over the VIF.
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.
✓
Verify that the on-premises router is advertising the VPC CIDR to the Direct Connect router.
Why this is correct
The on-premises router must advertise the VPC CIDR for return traffic.
Related concept
Read the scenario before looking for a memorised answer.
✗
Check that the NACLs on the EC2 instance's subnet allow inbound ICMP.
Why it's wrong here
NACLs are stateless and may block traffic, but the question states routes are correct.
✗
Confirm that the private VIF is associated with the correct virtual private gateway.
Why it's wrong here
The VIF is already configured and ping to Amazon side works.
✗
Ensure that BGP is established and receiving routes.
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume BGP being established (as evidenced by a successful ping to the VIF Amazon side IP) means all routing is correct, but they overlook the requirement for the on-premises router to advertise the VPC CIDR to enable return traffic.
Detailed technical explanation
How to think about this question
In a Direct Connect private VIF, BGP is used to exchange routing information between the on-premises router and the AWS Direct Connect router. The on-premises router must advertise the VPC CIDR (or a more specific prefix) to AWS so that the VGW can install a route in the VPC route tables pointing to the Direct Connect connection for return traffic. Without this advertisement, the VPC has no path to send packets back to the on-premises network, even though the forward path (on-premises to VPC) may work if static routes are used on the on-premises side. This is a common misconfiguration where BGP is up but the necessary prefix is not being advertised.
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 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: Verify that the on-premises router is advertising the VPC CIDR to the Direct Connect router. — The on-premises router can ping the VIF's Amazon side IP, confirming that Layer 2 and Layer 3 connectivity over the Direct Connect link is working, and BGP is established. However, the inability to ping the EC2 instance indicates that return traffic from the VPC is not reaching the on-premises network. For return traffic to be routed correctly, the on-premises router must advertise the VPC CIDR (or a specific prefix) to the Direct Connect router via BGP; otherwise, the AWS side will not forward traffic destined for the on-premises network over the VIF.
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.
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Question Discussion
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