The answer is to use IAM roles with the `compute.firewalls.create` permission at the host project level. This is correct because in a Shared VPC architecture, firewall rules are a host project resource, so controlling creation requires granting or denying the specific permission on that host project, not on the service project. By assigning a role like Compute Security Admin (which includes this permission) to specific service project identities, you can precisely restrict which service projects are allowed to create rules while blocking all others. On the Google Professional Cloud Network Engineer exam, this question tests your understanding of the Shared VPC permission model and the common trap of confusing host project versus service project IAM scopes—remember that network administration permissions live in the host project, not the service project. A helpful memory tip: think of the host project as the "gatekeeper" for all network resources; if you want to lock down firewall rule creation, you must apply the key (IAM permission) at the gate, not at the individual houses.
PCNE Implementing network security Practice Question
This PCNE practice question tests your understanding of implementing network security. 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.
An organization has a Shared VPC with several service projects. They want to restrict which service projects can create firewall rules in the host project. What should they do?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use IAM roles with compute.firewalls.create permission at the host project level.
Option A is correct because IAM roles with the `compute.firewalls.create` permission at the host project level allow you to precisely control which service projects can create firewall rules in the Shared VPC host project. By assigning a custom or predefined role (e.g., Compute Security Admin) that includes this permission to specific service project identities, you can restrict firewall rule creation to only authorized service projects while preventing others from doing so.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 IAM roles with compute.firewalls.create permission at the host project level.
Why this is correct
IAM allows fine-grained control over who can create firewall rules in the host project.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use VPC Service Controls.
Why it's wrong here
VPC Service Controls protect managed services, not firewall rule creation.
✗
Use hierarchical firewall policies.
Why it's wrong here
Hierarchical firewall policies set rules across projects, but do not restrict who can create rules.
✗
Use organization policies to deny firewall rule creation.
Why it's wrong here
Organization policies are not granular to specific service projects within a Shared VPC.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse VPC Service Controls or hierarchical firewall policies with IAM-based permission control, mistakenly thinking these features can restrict which service projects can create firewall rules, when they actually serve different purposes (data exfiltration prevention and rule enforcement, respectively).
Detailed technical explanation
How to think about this question
Under the hood, Shared VPC uses IAM roles at the host project level to delegate network administration to service projects. The `compute.firewalls.create` permission is part of the `compute.securityAdmin` role, which also includes `compute.firewalls.update` and `compute.firewalls.delete`. A common subtlety is that the service project must have the `compute.networks.updatePolicy` permission on the host project's VPC network to modify firewall rules, which is automatically included in the `compute.securityAdmin` role. In a real-world scenario, you might assign this role to a service project's service account to allow automated firewall rule creation via Infrastructure as Code (e.g., Terraform) while preventing manual changes from other projects.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Implementing network security — This question tests Implementing network security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use IAM roles with compute.firewalls.create permission at the host project level. — Option A is correct because IAM roles with the `compute.firewalls.create` permission at the host project level allow you to precisely control which service projects can create firewall rules in the Shared VPC host project. By assigning a custom or predefined role (e.g., Compute Security Admin) that includes this permission to specific service project identities, you can restrict firewall rule creation to only authorized service projects while preventing others from doing so.
What should I do if I get this PCNE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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