The correct answer is to add specific routes for S3 public IP prefixes pointing to the internet gateway. This works because of the longest prefix match rule in AWS route tables: a more specific route to the S3 prefixes (e.g., a /32 or a range from the S3 IP list) will override the general 10.0.0.0/8 route learned over Direct Connect via the virtual private gateway, forcing S3 traffic out to the internet instead. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of how to selectively override default or BGP-advertised routes without breaking connectivity to on-premises networks. A common trap is assuming you can simply delete the Direct Connect route or change the VPC CIDR, but neither is valid—you must add explicit, more specific routes. Memory tip: think of it as "specific beats general"—the IGW route for S3 is the narrowest path, so it wins every time.
ANS-C01 Network Implementation Practice Question
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 VIF to a VPC. The VPC has a virtual private gateway (VGW) attached. The on-premises network advertises a prefix 10.0.0.0/8 over BGP. The VPC has subnets with CIDR 10.0.1.0/24 and 10.0.2.0/24. The company wants to ensure that traffic to on-premises uses Direct Connect. However, traffic to an S3 bucket uses the internet. What route configuration is required?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add specific routes for S3 public IP prefixes pointing to the internet gateway.
Option D is correct because adding a specific route for S3 prefixes to the internet gateway will override the more general route through the VGW for those destinations. Option A is wrong because S3 traffic would go through Direct Connect. Option B is wrong because VPC CIDR cannot be changed. Option C is wrong because more specific routes to IGW are needed.
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.
✗
Change the VPC CIDR to avoid overlap with on-premises.
Why it's wrong here
Overlap is not the issue; routing decision is.
✓
Add specific routes for S3 public IP prefixes pointing to the internet gateway.
Why this is correct
More specific routes override the general route to VGW, directing S3 traffic to IGW.
Add a static route for 0.0.0.0/0 pointing to the internet gateway.
Why it's wrong here
This sends all internet traffic via IGW, but on-premises traffic would also go to IGW, not Direct Connect.
✗
Add a static route in the VPC route table for 0.0.0.0/0 pointing to the VGW.
Why it's wrong here
This sends all traffic including S3 through Direct Connect.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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: Add specific routes for S3 public IP prefixes pointing to the internet gateway. — Option D is correct because adding a specific route for S3 prefixes to the internet gateway will override the more general route through the VGW for those destinations. Option A is wrong because S3 traffic would go through Direct Connect. Option B is wrong because VPC CIDR cannot be changed. Option C is wrong because more specific routes to IGW are needed.
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.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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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 has a Direct Connect connection with a private VIF to a VPC. The on-premises network is advertising a default route (0.0.0.0/0) over BGP. The VPC has an internet gateway attached. When an EC2 instance in the VPC sends traffic to an internet destination, which path does it take by default?
hard
A.Traffic goes to the on-premises network only if there is a static route.
B.Traffic is dropped because there is no route.
C.Traffic goes to the internet via the internet gateway.
✓ D.Traffic goes to the on-premises network via Direct Connect.
Why D: Option A is correct because the VPC route table will have the more specific local VPC routes and the propagated route from Direct Connect. The most specific route for 0.0.0.0/0 will be the one from Direct Connect (propagated), so traffic goes to on-premises. Option B is wrong because the IGW route is not present. Option C is wrong because the instance sends traffic based on route table. Option D is wrong because traffic goes to on-premises.
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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
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