Quick Answer
The answer is to use an Organization Policy with the constraint `compute.vmExternalIpAccess`. This native Google Cloud policy is the best way to enforce no public IP with org policy because it operates at the resource creation level, explicitly denying any Compute Engine instance from being assigned an external IP address, and it cannot be bypassed by project-level IAM permissions. On the Google Professional Cloud Security Engineer exam, this question tests your understanding of preventive controls versus detective controls; a common trap is choosing a VPC firewall rule or a custom IAM role, but those only block traffic or restrict permissions after the fact, whereas the org policy prevents the public IP from ever existing. Remember the memory tip: “Org policy stops the IP at the door, firewalls just guard the floor.”
This PCSE practice question tests your understanding of configuring network security. 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.
Your organization wants to ensure that no Compute Engine instance can have a public IP address. What is the best way to enforce this policy?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Use Cloud Audit Logs to monitor and alert on instances with public IPs
Why wrong: Detective, not preventive.
Use an Organization Policy with the constraint `compute.vmExternalIpAccess`
Prevents creation of VMs with external IPs.
Use a firewall rule that blocks traffic from 0.0.0.0/0
Why wrong: Does not prevent assigning a public IP.
Use a Service Perimeter from VPC Service Controls
Why wrong: Controls data exfiltration, not VM public IP.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Use an Organization Policy with the constraint `compute.vmExternalIpAccess`
Option B is correct because the Organization Policy constraint `compute.vmExternalIpAccess` is a native Google Cloud policy that can be applied at the project, folder, or organization level to explicitly deny the assignment of external IP addresses to Compute Engine instances. This policy is enforced at the resource creation time, preventing any instance from being launched with a public IP, and it cannot be overridden by project-level IAM permissions, making it the most direct and effective enforcement mechanism.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Use Cloud Audit Logs to monitor and alert on instances with public IPs
Why it's wrong here
Detective, not preventive.
Use an Organization Policy with the constraint `compute.vmExternalIpAccess`
Why this is correct
Prevents creation of VMs with external IPs.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Use a firewall rule that blocks traffic from 0.0.0.0/0
Why it's wrong here
Does not prevent assigning a public IP.
Use a Service Perimeter from VPC Service Controls
Why it's wrong here
Controls data exfiltration, not VM public IP.
Common exam traps
The trap here is that candidates often confuse reactive monitoring (Cloud Audit Logs) or network-layer controls (firewall rules) with proactive policy enforcement, or they misapply VPC Service Controls, which are for data exfiltration prevention, not for controlling instance-level network interface configurations.
Detailed technical explanation
The `compute.vmExternalIpAccess` constraint is part of Google Cloud's Organization Policy Service and uses a deny-list approach: by default, external IPs are allowed, but the policy can be set to block them for all instances or allow only specific VMs via a list of exceptions. Under the hood, this constraint is evaluated during the instance creation API call (e.g., `instances.insert`), and if the policy denies external IPs, the request fails with a `403` error, even if the user has `compute.instances.create` permission. A real-world scenario is a financial services company that must comply with PCI DSS requirements, where no compute resource should be directly accessible from the internet; this policy ensures that even a developer with broad IAM roles cannot accidentally create a publicly exposed instance.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Configuring network security — This question tests Configuring network security — Read the scenario before looking for a memorised answer..
The correct answer is: Use an Organization Policy with the constraint `compute.vmExternalIpAccess` — Option B is correct because the Organization Policy constraint `compute.vmExternalIpAccess` is a native Google Cloud policy that can be applied at the project, folder, or organization level to explicitly deny the assignment of external IP addresses to Compute Engine instances. This policy is enforced at the resource creation time, preventing any instance from being launched with a public IP, and it cannot be overridden by project-level IAM permissions, making it the most direct and effective enforcement mechanism.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This PCSE 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 PCSE exam.
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