The correct answer is to use an IAM role (instance profile) attached to the EC2 instance with permissions for the S3 bucket, alongside VPC endpoint policies and S3 bucket policies that restrict access based on source VPC or VPC endpoint. This combination works because IAM roles grant temporary credentials to the EC2 instance, while VPC endpoint policies act as a gatekeeper for traffic through the endpoint, and S3 bucket policies can enforce conditions like the source VPC ID, creating a layered defense. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your understanding of how to restrict S3 access from EC2 instances without relying on security groups or network ACLs, which do not apply to S3 traffic. A common trap is assuming network ACLs or security groups can filter S3 access, but they operate at the subnet or instance level and cannot see S3 bucket identifiers. Remember the mnemonic “VIP” for the three valid methods: VPC endpoint policies, Instance profiles (IAM roles), and S3 bucket Policies.
ANS-C01 Network Security, Compliance and Governance Practice Question
This ANS-C01 practice question tests your understanding of network security, compliance and governance. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Which THREE of the following are valid ways to restrict access to an S3 bucket that is accessed by EC2 instances in a VPC?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use an S3 bucket policy that restricts access to the VPC or VPC endpoint.
Options A, B, and C are correct. Option A: VPC endpoint policies can restrict access to specific S3 buckets. Option B: S3 bucket policies can restrict access based on source VPC or source VPC endpoint. Option C: Instance profiles grant IAM roles to EC2 instances, which can be used with S3 bucket policies. Option D is wrong: Security groups do not apply to S3 bucket access. Option E is wrong: Network ACLs operate at the subnet level and do not filter by S3 bucket.
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.
✓
Use an S3 bucket policy that restricts access to the VPC or VPC endpoint.
Why this is correct
S3 bucket policies can use aws:SourceVpc or aws:SourceVpce conditions.
Use a security group to allow outbound traffic from the EC2 instance to the S3 bucket.
Why it's wrong here
Security groups do not filter by S3 bucket; they filter by IP.
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 Security, Compliance and Governance — This question tests Network Security, Compliance and Governance — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Use an S3 bucket policy that restricts access to the VPC or VPC endpoint. — Options A, B, and C are correct. Option A: VPC endpoint policies can restrict access to specific S3 buckets. Option B: S3 bucket policies can restrict access based on source VPC or source VPC endpoint. Option C: Instance profiles grant IAM roles to EC2 instances, which can be used with S3 bucket policies. Option D is wrong: Security groups do not apply to S3 bucket access. Option E is wrong: Network ACLs operate at the subnet level and do not filter by S3 bucket.
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.
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Question Discussion
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