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 has a Direct Connect connection with a private virtual interface (VIF) to a VPC. They have also set up a Site-to-Site VPN as a backup. The VPC has a virtual private gateway (VGW) attached. The on-premises network uses BGP over the Direct Connect and static routes for the VPN. The network engineer notices that traffic from the VPC to on-premises is not using the Direct Connect when it is available; instead, it goes over the VPN. The VPC route table has a route for the on-premises CIDR (10.0.0.0/8) to the VGW. The VPN connection is configured with static routes. What is the MOST likely cause of this behavior?
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 VPN static route has higher precedence than the BGP route from Direct Connect
Option D is correct. When using a VGW, AWS automatically propagates routes from the Direct Connect virtual interface and the VPN connection into the VPC route table. If both routes are propagated, the VPN route (static) may have a lower metric or be preferred due to BGP attributes? Actually, by default, AWS prefers the more specific route. But here both are to the same CIDR? The on-premises CIDR is 10.0.0.0/8. The Direct Connect virtual interface advertises this via BGP. The VPN static route also specifies this CIDR. AWS route tables use the longest prefix match, but if both routes have the same prefix length, the one with the lower BGP metric (if BGP) or the static route? Actually, static routes have higher precedence than propagated routes. So the static route from the VPN would be preferred over the BGP route from Direct Connect. That is the issue. The engineer should either remove the static route from the VPN or use BGP on the VPN to allow path selection. Option A is incorrect because both are to the VGW. Option B is incorrect because the VGW is attached. Option C is incorrect because the VPC route table does have a route.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 VPN static route has higher precedence than the BGP route from Direct Connect
Why this is correct
Correct; static routes (from VPN) are preferred over BGP propagated routes in AWS route tables.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The VPC route table does not have a route for the on-premises CIDR
Why it's wrong here
Incorrect; it does have a route.
✗
The VGW is not attached to the VPC
Why it's wrong here
Incorrect; the VGW is attached.
✗
The Direct Connect virtual interface is not associated with the VGW
Why it's wrong here
Incorrect; the VGW is attached and the VIF is associated.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Network Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The VPN static route has higher precedence than the BGP route from Direct Connect — Option D is correct. When using a VGW, AWS automatically propagates routes from the Direct Connect virtual interface and the VPN connection into the VPC route table. If both routes are propagated, the VPN route (static) may have a lower metric or be preferred due to BGP attributes? Actually, by default, AWS prefers the more specific route. But here both are to the same CIDR? The on-premises CIDR is 10.0.0.0/8. The Direct Connect virtual interface advertises this via BGP. The VPN static route also specifies this CIDR. AWS route tables use the longest prefix match, but if both routes have the same prefix length, the one with the lower BGP metric (if BGP) or the static route? Actually, static routes have higher precedence than propagated routes. So the static route from the VPN would be preferred over the BGP route from Direct Connect. That is the issue. The engineer should either remove the static route from the VPN or use BGP on the VPN to allow path selection. Option A is incorrect because both are to the VGW. Option B is incorrect because the VGW is attached. Option C is incorrect because the VPC route table does have a route.
What should I do if I get this ANS-C01 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
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?
CIDR notation defines the prefix length.
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