The answer is that the domain must be added to a private DNS zone. This is correct because Private Google Access enables instances without public IPs to reach Google APIs using internal IPs, but it relies on DNS resolution pointing to the private IP range 199.36.153.8/30. Without a private DNS zone, such as googleapis.com, configured in the VPC, DNS queries for storage.googleapis.com will resolve to public IPs, breaking connectivity. On the Google Professional Cloud Security Engineer exam, this tests your understanding of how Private Google Access integrates with Cloud DNS and VPC networking—a common trap is assuming enabling the subnet-level setting alone is sufficient. Remember: Private Google Access opens the network path, but DNS must be the map; without the private zone, your instances are looking for public addresses on a private road. Memory tip: "PGA needs a DNS zone—no zone, no phone."
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.
Exhibit
Refer to the exhibit.
```
$ gcloud compute networks subnets describe my-subnet --region=us-central1
cidr: 10.0.0.0/24
privateIpGoogleAccess: true
enableFlowLogs: true
```
An engineer has enabled Private Google Access on the subnet. However, instances in the subnet cannot access Google APIs (e.g., storage.googleapis.com) using their internal IPs. What is the most likely issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The domain needs to be added to a DNS zone
Private Google Access allows instances without public IPs to reach Google APIs and services using their internal IPs, but it requires that the DNS resolution for the API domain (e.g., storage.googleapis.com) resolves to the private IP range used by Google's Private Access (199.36.153.8/30). If the domain is not added to a private DNS zone (e.g., googleapis.com) in the VPC, DNS will resolve to public IPs, causing connectivity failure. Option B correctly identifies this missing DNS configuration as the most likely issue.
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.
✗
The instances need a public IP
Why it's wrong here
Private Google Access is specifically for instances without public IPs.
✓
The domain needs to be added to a DNS zone
Why this is correct
If using custom DNS, you must create a private zone for googleapis.com to resolve to the private IPs.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Private Google Access requires a VPC connector
Why it's wrong here
No additional connector is needed; it is a subnet-level attribute.
✗
The instances have no route to the default internet gateway
Why it's wrong here
Private Google Access does not require a default route; it uses Google's private network.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that Private Google Access requires a public IP or a VPC connector, when in fact the critical missing piece is the DNS configuration to resolve Google API domains to private IPs.
Detailed technical explanation
How to think about this question
Private Google Access works by routing traffic destined to Google API IPs (199.36.153.8/30) through the default internet gateway, but the gateway forwards it to Google's private network without requiring a public IP on the instance. The DNS resolution must be overridden using a private DNS zone (e.g., googleapis.com) with A records pointing to 199.36.153.8 or 199.36.153.9, or using a forwarding zone to Google's internal DNS servers. In real-world scenarios, failing to configure this DNS zone is the most common misconfiguration, as engineers often assume that enabling Private Google Access on the subnet automatically handles DNS.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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: The domain needs to be added to a DNS zone — Private Google Access allows instances without public IPs to reach Google APIs and services using their internal IPs, but it requires that the DNS resolution for the API domain (e.g., storage.googleapis.com) resolves to the private IP range used by Google's Private Access (199.36.153.8/30). If the domain is not added to a private DNS zone (e.g., googleapis.com) in the VPC, DNS will resolve to public IPs, causing connectivity failure. Option B correctly identifies this missing DNS configuration as the most likely issue.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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