- A
OS-level host-based firewalls on each VM
Why wrong: While important, host-based firewalls are compute instance security, not a network-level control.
- B
VPC firewall rules to restrict traffic between subnets
VPC firewall rules are a fundamental network security control to filter traffic.
- C
IAM roles to control who can create Compute Engine instances
Why wrong: IAM is an identity and access management control, not a network security control.
- D
Workload Identity Federation to allow workloads to authenticate to Google APIs
Why wrong: This is an identity and access management feature, not a network security control.
- E
Cloud Armor to protect against DDoS and web application attacks
Cloud Armor is a network security service that provides WAF and DDoS protection at the edge.
Quick Answer
The correct answers are VPC firewall rules and Cloud Armor, as these two controls implement defense in depth for network security in Google Cloud by operating at different layers of the stack. VPC firewall rules enforce network segmentation and micro-segmentation by restricting traffic between subnets based on source and destination IP ranges, protocols, and ports, which is a fundamental principle of defense in depth. Cloud Armor adds a perimeter defense by providing Web Application Firewall (WAF) capabilities and DDoS protection at Google’s edge, filtering malicious traffic before it reaches your load balancers or VMs. On the Google Professional Cloud Security Engineer exam, this question tests your ability to distinguish between network-level controls (firewall rules) and application-edge controls (Cloud Armor), with a common trap being to select a single control like Cloud NAT or Private Google Access, which do not directly filter or block threats. Remember the memory tip: “Firewall for the floor, Armor for the door”—firewall rules segment inside your VPC, while Cloud Armor guards the entry point.
PCSE Configuring network security Practice Question
This PCSE practice question tests your understanding of configuring 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.
You are a security engineer for a company that runs a critical application on Google Cloud. You need to implement defense in depth for network security. Which TWO of the following are effective network security controls that you should implement?
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
VPC firewall rules to restrict traffic between subnets
VPC firewall rules (B) are a fundamental network security control that allow you to restrict traffic between subnets based on source/destination IP ranges, protocols, and ports. This implements network segmentation and micro-segmentation, which is a core principle of defense in depth. Cloud Armor (E) provides Web Application Firewall (WAF) capabilities and DDoS protection at the edge of Google's network, filtering malicious traffic before it reaches your VMs or load balancers.
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.
- ✗
OS-level host-based firewalls on each VM
Why it's wrong here
While important, host-based firewalls are compute instance security, not a network-level control.
- ✓
VPC firewall rules to restrict traffic between subnets
Why this is correct
VPC firewall rules are a fundamental network security control to filter traffic.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
IAM roles to control who can create Compute Engine instances
Why it's wrong here
IAM is an identity and access management control, not a network security control.
- ✗
Workload Identity Federation to allow workloads to authenticate to Google APIs
Why it's wrong here
This is an identity and access management feature, not a network security control.
- ✓
Cloud Armor to protect against DDoS and web application attacks
Why this is correct
Cloud Armor is a network security service that provides WAF and DDoS protection at the edge.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between network security controls (which filter traffic at the network layer) and host/identity/authentication controls, so candidates mistakenly select IAM or Workload Identity Federation because they think 'access control' equals network security.
Detailed technical explanation
How to think about this question
VPC firewall rules are stateful and evaluated in order of priority (lowest number first), with an implicit deny-all at the end; they can be applied to VMs via network tags or service accounts for dynamic segmentation. Cloud Armor uses Google's global infrastructure to absorb DDoS attacks at the edge and supports custom rules based on Layer 7 attributes like request headers, URI paths, and IP reputation lists. Defense in depth for network security requires controls at multiple layers: edge (Cloud Armor), network (VPC firewall rules), and host (OS firewall), but the question specifically asks for network security controls, not host or identity controls.
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.
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FAQ
Questions learners often ask
What does this PCSE question test?
Configuring network security — This question tests Configuring network security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: VPC firewall rules to restrict traffic between subnets — VPC firewall rules (B) are a fundamental network security control that allow you to restrict traffic between subnets based on source/destination IP ranges, protocols, and ports. This implements network segmentation and micro-segmentation, which is a core principle of defense in depth. Cloud Armor (E) provides Web Application Firewall (WAF) capabilities and DDoS protection at the edge of Google's network, filtering malicious traffic before it reaches your VMs or load balancers.
What should I do if I get this PCSE 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.
About these practice questions
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Last reviewed: Jun 30, 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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