The answer is to combine VPC Service Controls with a Cloud Firewall that denies egress to non-Google IPs. This configuration works because VPC Service Controls create a data perimeter that restricts access to Google Cloud Storage from within the allowed context, while the Cloud Firewall egress rule physically blocks traffic destined for external IP ranges like those of AWS S3. Together, they provide a defense-in-depth approach: VPC-SC prevents data from leaving the perimeter via Google APIs, and the firewall stops the network-level exfiltration attempt before it even reaches the external service. On the Google Professional Cloud Network Engineer exam, this question tests your understanding that VPC-SC alone cannot block egress to non-Google IPs—it only controls access to Google APIs. A common trap is assuming VPC-SC alone is sufficient, but the firewall rule is essential for blocking external cloud storage endpoints. Memory tip: think of VPC-SC as the “door lock” on Google services and the firewall as the “fence” blocking the path to non-Google IPs.
PCNE Implementing network security Practice Question
This PCNE practice question tests your understanding of implementing network security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
An organization wants to restrict data exfiltration from a GCP project. They need to prevent users from copying data to external cloud storage services like AWS S3, but allow access to Google Cloud Storage. Which VPC Service Controls (VPC-SC) configuration should they use?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Combine VPC Service Controls with a Cloud Firewall that denies egress to non-Google IPs.
Option A is correct because VPC Service Controls (VPC-SC) can create a perimeter that restricts data movement to only Google Cloud Storage, while Cloud Firewall egress rules can deny traffic to non-Google IP ranges (including AWS S3 endpoints). This combination ensures that even if a user attempts to copy data to an external cloud storage service, the firewall blocks the egress traffic, and VPC-SC prevents access to Google Cloud Storage from outside the perimeter.
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.
✓
Combine VPC Service Controls with a Cloud Firewall that denies egress to non-Google IPs.
Why this is correct
VPC-SC secures Google services, and firewall rules can block external destinations.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use Cloud Firewall rules to block egress to AWS IP ranges.
Why it's wrong here
While helpful, this does not prevent data exfiltration via other Google services.
✗
Enable Data Loss Prevention (DLP) API to inspect outgoing data.
Why it's wrong here
DLP is not a network security control for blocking services.
✗
Create a VPC Service Controls perimeter that includes the project and set access levels to allow only Google Cloud Storage.
Why it's wrong here
VPC-SC only controls access to Google Cloud services, not external services like AWS S3.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that VPC Service Controls alone can block data exfiltration to external cloud storage services, when in fact they only control access to Google Cloud services and must be combined with network-level controls like Cloud Firewall egress rules to block traffic to non-Google endpoints.
Detailed technical explanation
How to think about this question
VPC Service Controls use context-aware access policies to create perimeters around Google Cloud services, preventing data from being copied to resources outside the perimeter. Cloud Firewall egress rules operate at the network layer (Layer 3/4) and can block traffic to specific IP ranges, but they cannot inspect application-layer protocols like HTTPS to differentiate between Google Cloud Storage and AWS S3. In a real-world scenario, an organization might combine VPC-SC with Cloud NAT and firewall rules to ensure that all egress traffic to non-Google IPs is denied, while allowing internal Google Cloud Storage access through private Google access.
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.
Implementing network security — This question tests Implementing network security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Combine VPC Service Controls with a Cloud Firewall that denies egress to non-Google IPs. — Option A is correct because VPC Service Controls (VPC-SC) can create a perimeter that restricts data movement to only Google Cloud Storage, while Cloud Firewall egress rules can deny traffic to non-Google IP ranges (including AWS S3 endpoints). This combination ensures that even if a user attempts to copy data to an external cloud storage service, the firewall blocks the egress traffic, and VPC-SC prevents access to Google Cloud Storage from outside the perimeter.
What should I do if I get this PCNE 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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