- A
The S3 gateway endpoint is not in the same VPC.
Why wrong: The endpoint is created in the same VPC, but the route is missing.
- B
The S3 bucket policy does not allow access from the VPC.
Why wrong: Bucket policy is for cross-account or specific conditions; the gateway endpoint policy is the primary control.
- C
The NAT Gateway is in a different availability zone than the private instances.
Why wrong: NAT Gateway is used for internet access; S3 gateway endpoint does not use NAT.
- D
The private subnet's route table does not have a route to the S3 gateway endpoint.
Without a route to the endpoint, traffic to S3 goes through the NAT Gateway or is dropped.
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 VPC with public and private subnets. The public subnet has a NAT Gateway, and the private subnet has EC2 instances that need internet access. The private instances can reach the internet, but cannot access an S3 bucket in the same region using the S3 gateway endpoint. 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 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 private subnet's route table does not have a route to the S3 gateway endpoint.
For private instances to use a gateway endpoint, the route table for the private subnet must have a route pointing to the S3 endpoint. Additionally, the endpoint's policy must allow the traffic. The NAT Gateway is not used for gateway endpoints.
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 S3 gateway endpoint is not in the same VPC.
Why it's wrong here
The endpoint is created in the same VPC, but the route is missing.
- ✗
The S3 bucket policy does not allow access from the VPC.
Why it's wrong here
Bucket policy is for cross-account or specific conditions; the gateway endpoint policy is the primary control.
- ✗
The NAT Gateway is in a different availability zone than the private instances.
- ✓
The private subnet's route table does not have a route to the S3 gateway endpoint.
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.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Management and Operations — This question tests Network Management and Operations — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The private subnet's route table does not have a route to the S3 gateway endpoint. — For private instances to use a gateway endpoint, the route table for the private subnet must have a route pointing to the S3 endpoint. Additionally, the endpoint's policy must allow the traffic. The NAT Gateway is not used for gateway endpoints.
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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Last reviewed: Jun 20, 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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