- A
Assign a unique service account to the instances and use IAM conditions to allow the service account access to the bucket only when connecting from the VPC network.
Why wrong: IAM conditions can check the source IP, but with Private Google Access, the source IP is internal, so this is less effective.
- B
Enable Private Google Access on the subnet and use VPC Service Controls with a service perimeter that includes the VPC and the Cloud Storage bucket.
VPC Service Controls provide a security perimeter around Google APIs, restricting access from unauthorized networks.
- C
Configure a firewall rule that allows egress traffic to the Cloud Storage API only from the instances' subnet.
Why wrong: Firewall rules control network traffic but do not enforce access control on the API itself.
- D
Create an IAM condition that restricts access based on the instance's internal IP address range.
Why wrong: Internal IPs can be spoofed or changed; IAM conditions are not the strongest mechanism for network-level restrictions.
PCNE Implementing VPC Instances Practice Question
This PCNE practice question tests your understanding of implementing vpc instances. 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.
A network engineer wants to restrict access to a Cloud Storage bucket from only a specific set of Compute Engine instances in a VPC. The instances have no external IPs. What is the most effective way to enforce this restriction?
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
Enable Private Google Access on the subnet and use VPC Service Controls with a service perimeter that includes the VPC and the Cloud Storage bucket.
Using Private Google Access with Private Service Connect allows instances to reach Google APIs via internal IPs. By using VPC Service Controls, you can create a service perimeter that restricts access to the Cloud Storage bucket from the specific VPC and projects. This provides a defense-in-depth approach.
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.
- ✗
Assign a unique service account to the instances and use IAM conditions to allow the service account access to the bucket only when connecting from the VPC network.
Why it's wrong here
IAM conditions can check the source IP, but with Private Google Access, the source IP is internal, so this is less effective.
- ✓
Enable Private Google Access on the subnet and use VPC Service Controls with a service perimeter that includes the VPC and the Cloud Storage bucket.
Why this is correct
VPC Service Controls provide a security perimeter around Google APIs, restricting access from unauthorized networks.
Related concept
CIDR notation defines the prefix length.
- ✗
Configure a firewall rule that allows egress traffic to the Cloud Storage API only from the instances' subnet.
Why it's wrong here
Firewall rules control network traffic but do not enforce access control on the API itself.
- ✗
Create an IAM condition that restricts access based on the instance's internal IP address range.
Why it's wrong here
Internal IPs can be spoofed or changed; IAM conditions are not the strongest mechanism for network-level restrictions.
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 PCNE subnetting questions on CIDR, address ranges, and subnet selection.
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Implementing VPC Instances — study guide chapter
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FAQ
Questions learners often ask
What does this PCNE question test?
Implementing VPC Instances — This question tests Implementing VPC Instances — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Enable Private Google Access on the subnet and use VPC Service Controls with a service perimeter that includes the VPC and the Cloud Storage bucket. — Using Private Google Access with Private Service Connect allows instances to reach Google APIs via internal IPs. By using VPC Service Controls, you can create a service perimeter that restricts access to the Cloud Storage bucket from the specific VPC and projects. This provides a defense-in-depth approach.
What should I do if I get this PCNE 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 PCNE 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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Last reviewed: Jul 4, 2026
This PCNE practice question is part of Courseiva's free Google Cloud 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 PCNE exam.
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