PCSE Configuring network security Practice Question
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.
A company has a VPC with subnet-a (10.0.1.0/24) and subnet-b (10.0.2.0/24). They enabled Private Google Access on subnet-a. Instances in subnet-a can access Google APIs and services using private IPs. However, instances in subnet-b cannot reach Google APIs even though subnet-b has a default route to the internet through a NAT gateway. What is the likely cause?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Private Google Access is not enabled on subnet-b.
Private Google Access is a per-subnet setting that allows instances with only private IPs to reach Google APIs and services through the VPC's default internet gateway, without needing public IPs or NAT. Since subnet-b does not have Private Google Access enabled, its instances cannot use this feature even though they have a default route to the internet via a NAT gateway; the NAT gateway only provides outbound internet access for public IP destinations, not the private IP ranges used by Google APIs.
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.
✗
Subnet-b does not have a default route to the internet.
Incorrect: Cloud NAT is for internet, not private Google access.
✗
Firewall rules are blocking traffic to googleapis.com.
Why it's wrong here
Incorrect: firewall rules likely allow egress, but private Google access requires subnet-level config.
✓
Private Google Access is not enabled on subnet-b.
Why this is correct
Correct: must enable per subnet.
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 misconception that a NATgateway or internet gateway alone is sufficient for accessing Google APIs, when in fact Private Google Access must be explicitly enabled on each subnet that requires it.
Detailed technical explanation
How to think about this question
Private Google Access works by using the VPC's default internet gateway to route traffic destined for Google API IP addresses (which are published in Google's DNS as private IP ranges, e.g., 199.36.153.4/30 for restricted.googleapis.com) through Google's backbone, bypassing the public internet. This requires the subnet to have the 'privateIpGoogleAccess' flag set to true; without it, the VPC router will not forward traffic from that subnet to the internet gateway for Google API destinations, even if a default route exists. In contrast, Cloud NAT is used for outbound connections to the public internet from instances without public IPs, but it does not enable access to Google APIs via private IPs.
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.
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: Private Google Access is not enabled on subnet-b. — Private Google Access is a per-subnet setting that allows instances with only private IPs to reach Google APIs and services through the VPC's default internet gateway, without needing public IPs or NAT. Since subnet-b does not have Private Google Access enabled, its instances cannot use this feature even though they have a default route to the internet via a NAT gateway; the NAT gateway only provides outbound internet access for public IP destinations, not the private IP ranges used by Google APIs.
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.
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Question Discussion
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