- A
Create a VPC firewall rule that denies ingress from the region's IP ranges.
Why wrong: VPC firewall rules apply to instance-level traffic, but for an external load balancer, the traffic arrives with the load balancer's source IP (the load balancer frontend), not the client's original IP. Thus, VPC firewall rules cannot see the client IP and cannot block based on geolocation.
- B
Use Identity-Aware Proxy (IAP) to block access based on the user's location.
Why wrong: IAP controls access based on identity and context, but it does not block traffic at the network level; it works with authentication.
- C
Configure a Cloud CDN policy to block traffic from certain regions.
Why wrong: Cloud CDN caches content and does not provide geo-blocking capabilities; Cloud Armor is needed for that.
- D
Create a Cloud Armor security policy with a geo-based deny rule and attach it to the load balancer.
Correct: Cloud Armor can inspect client IPs even behind a load balancer and apply geo-blocking rules.
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.
A security engineer needs to block traffic from all IP addresses in a specific geographic region from reaching an HTTPS load-balanced application. The application uses Cloud Load Balancing with an external HTTPS load balancer. Which approach should the engineer use?
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
Create a Cloud Armor security policy with a geo-based deny rule and attach it to the load balancer.
Cloud Armor security policies can be attached to external HTTPS load balancers to filter traffic based on geolocation. The engineer can create a Cloud Armor security policy with a rule that uses the geo-tag to deny traffic from the specified region.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a VPC firewall rule that denies ingress from the region's IP ranges.
Why it's wrong here
VPC firewall rules apply to instance-level traffic, but for an external load balancer, the traffic arrives with the load balancer's source IP (the load balancer frontend), not the client's original IP. Thus, VPC firewall rules cannot see the client IP and cannot block based on geolocation.
- ✗
Use Identity-Aware Proxy (IAP) to block access based on the user's location.
Why it's wrong here
IAP controls access based on identity and context, but it does not block traffic at the network level; it works with authentication.
- ✗
Configure a Cloud CDN policy to block traffic from certain regions.
Why it's wrong here
Cloud CDN caches content and does not provide geo-blocking capabilities; Cloud Armor is needed for that.
- ✓
Create a Cloud Armor security policy with a geo-based deny rule and attach it to the load balancer.
Why this is correct
Correct: Cloud Armor can inspect client IPs even behind a load balancer and apply geo-blocking rules.
Related concept
Standard ACLs match source addresses.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
- Standard ACLs match source addresses.
- Extended ACLs can match source, destination, protocol and ports.
- The first matching ACL entry is used.
- There is usually an implicit deny at the end.
TExam Day Tips
- Check inbound versus outbound direction.
- Read the ACL from top to bottom.
- Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Visual reference
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PCSE ACL questions on filtering logic and placement.
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FAQ
Questions learners often ask
What does this PCSE question test?
Configuring Network Security — This question tests Configuring Network Security — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Create a Cloud Armor security policy with a geo-based deny rule and attach it to the load balancer. — Cloud Armor security policies can be attached to external HTTPS load balancers to filter traffic based on geolocation. The engineer can create a Cloud Armor security policy with a rule that uses the geo-tag to deny traffic from the specified region.
What should I do if I get this PCSE question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PCSE ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Last reviewed: Jul 4, 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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