- A
Attach each service project to one host project network and use IAM roles to grant access to specific subnets in other networks with a cross-project service account.
This allows service projects to access multiple networks by using IAM on subnets and service accounts, minimizing firewall rules.
- B
Use VPC Network Peering between each service project's VPC and the host project's networks.
Why wrong: Peering adds complexity and does not provide centralized IAM control; also, each service project needs its own VPC.
- C
Create a separate host project for each environment and attach service projects accordingly.
Why wrong: This increases management overhead and does not minimize firewall rules.
- D
Create a single VPC network that encompasses all environments, and use subnet-level firewall rules to isolate environments.
Why wrong: This does not provide separate VPC networks per environment, which may be a compliance requirement.
Quick Answer
The answer is to attach each service project to one host project network and use IAM roles to grant access to specific subnets in other networks with a cross-project service account. This approach is correct because Shared VPC enforces a one-to-one attachment between a service project and a single VPC network in the host project; a service project cannot natively span multiple networks. To implement Shared VPC with IAM for granular subnet access across multiple service projects, you leverage subnet-level IAM roles like `compute.networkUser` to grant a service project’s resources access to subnets in other networks, while keeping firewall rules minimal and centralized. On the Google Professional Cloud Network Engineer exam, this tests your understanding of Shared VPC’s attachment limitation and IAM’s ability to override network boundaries—a common trap is assuming a service project can attach to multiple networks directly. Memory tip: “One network per project, IAM for the rest.”
PCNE Implementing a Virtual Private Cloud Practice Question
This PCNE practice question tests your understanding of implementing a virtual private cloud. 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 company is designing a Shared VPC architecture for multiple projects. The host project hosts three VPC networks: 'prod', 'staging', 'dev'. Each service project needs access to a specific network. Some service projects require access to multiple networks. The security team wants to minimize the number of firewall rules and use IAM for centralized control. Which approach meets these requirements?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"minimum / minimize"Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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
Attach each service project to one host project network and use IAM roles to grant access to specific subnets in other networks with a cross-project service account.
Shared VPC allows service projects to be attached to a single host project, but a service project can only be attached to one VPC network in the host project. To access multiple networks, the service project must be attached to multiple host projects or use separate networks per project. Using IAM at the subnet level with roles like compute.networkUser allows granular access. Option C is correct because it limits service projects to one network each and uses IAM to grant cross-network access as 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.
- ✓
Attach each service project to one host project network and use IAM roles to grant access to specific subnets in other networks with a cross-project service account.
- ✗
Use VPC Network Peering between each service project's VPC and the host project's networks.
Why it's wrong here
Peering adds complexity and does not provide centralized IAM control; also, each service project needs its own VPC.
- ✗
Create a separate host project for each environment and attach service projects accordingly.
Why it's wrong here
This increases management overhead and does not minimize firewall rules.
- ✗
Create a single VPC network that encompasses all environments, and use subnet-level firewall rules to isolate environments.
Why it's wrong here
This does not provide separate VPC networks per environment, which may be a compliance requirement.
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 PCNE subnetting questions on CIDR, address ranges, and subnet selection.
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Implementing a Virtual Private Cloud — study guide chapter
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FAQ
Questions learners often ask
What does this PCNE question test?
Implementing a Virtual Private Cloud — This question tests Implementing a Virtual Private Cloud — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Attach each service project to one host project network and use IAM roles to grant access to specific subnets in other networks with a cross-project service account. — Shared VPC allows service projects to be attached to a single host project, but a service project can only be attached to one VPC network in the host project. To access multiple networks, the service project must be attached to multiple host projects or use separate networks per project. Using IAM at the subnet level with roles like compute.networkUser allows granular access. Option C is correct because it limits service projects to one network each and uses IAM to grant cross-network access as needed.
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.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Last reviewed: Jun 24, 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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