The answer is to enable Private Google Access on subnet-b. This is correct because Private Google Access allows VM instances with only internal IP addresses to reach Google APIs and services through Google’s private network via the default internet gateway, without needing an external IP. Since subnet-a already has this setting enabled, its VMs can route traffic privately to Google APIs, but subnet-b lacks it, so its VMs fail. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of how VPC subnet-level settings control API access; a common trap is assuming that a VM’s internal IP alone is sufficient, or confusing Private Google Access with Cloud NAT or VPC peering. Remember the key distinction: Private Google Access is a per-subnet toggle that must be explicitly enabled—it is not inherited from the VPC. A useful memory tip is “subnet switch for private API reach”—if a VM has no external IP, check that its subnet has Private Google Access turned on.
PCNE Configuring network services Practice Question
This PCNE practice question tests your understanding of configuring network services. 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 list
NAME REGION NETWORK RANGE PRIVATE_GOOGLE_ACCESS STACK_TYPE
subnet-a us-central1 vpc1 10.0.1.0/24 Enabled IPV4_ONLY
subnet-b us-east1 vpc1 10.0.2.0/24 Disabled IPV4_ONLY
A VM in 'subnet-a' can access Google APIs via private IP, but a VM in 'subnet-b' cannot.
Refer to the exhibit. A VM in 'subnet-a' can access Google APIs via private IP, but a VM in 'subnet-b' cannot. What change should be made to fix this?
Refer to the exhibit.
$ gcloud compute networks subnets list
NAME REGION NETWORK RANGE PRIVATE_GOOGLE_ACCESS STACK_TYPE
subnet-a us-central1 vpc1 10.0.1.0/24 Enabled IPV4_ONLY
subnet-b us-east1 vpc1 10.0.2.0/24 Disabled IPV4_ONLY
A VM in 'subnet-a' can access Google APIs via private IP, but a VM in 'subnet-b' cannot.
A
Change the stack type of subnet-b to IPV4_IPV6.
Why wrong: Stack type does not affect private access.
B
Configure Cloud NAT in the region of subnet-b.
Why wrong: Cloud NAT is for internet egress, not for private Google access.
C
Add a firewall rule allowing egress to 0.0.0.0/0 on port 443 for subnet-b.
Why wrong: Firewall rules do not enable Private Google Access.
D
Enable Private Google Access on subnet-b.
Enabling Private Google Access allows VMs to reach Google APIs via internal IP.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable Private Google Access on subnet-b.
Private Google Access enables a VM that has only an internal IP address (no external IP) to reach Google APIs and services through the default internet gateway using Google's private network. Since subnet-b lacks this setting, VMs there cannot reach Google APIs via private IP. Enabling Private Google Access on subnet-b resolves this by allowing the VM's traffic to be routed to Google APIs without needing an external IP.
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.
✗
Change the stack type of subnet-b to IPV4_IPV6.
Why it's wrong here
Stack type does not affect private access.
✗
Configure Cloud NAT in the region of subnet-b.
Why it's wrong here
Cloud NAT is for internet egress, not for private Google access.
✗
Add a firewall rule allowing egress to 0.0.0.0/0 on port 443 for subnet-b.
Why it's wrong here
Firewall rules do not enable Private Google Access.
✓
Enable Private Google Access on subnet-b.
Why this is correct
Enabling Private Google Access allows VMs to reach Google APIs via internal IP.
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 enabling outbound internet access (Cloud NAT) and enabling private access to Google services (Private Google Access), leading candidates to mistakenly choose Cloud NAT when the requirement is specifically for private IP access to Google APIs.
Detailed technical explanation
How to think about this question
Private Google Access works by adding a default route (0.0.0.0/0) with a next hop of 'default internet gateway' that is specifically configured to forward traffic to Google's private IP ranges (e.g., 199.36.153.4/30 for Google APIs) over Google's backbone, not the public internet. This is enabled per subnet via the 'privateIpGoogleAccess' field in the subnet resource. Without this setting, the subnet's default route sends traffic to the internet gateway, which requires an external IP for return traffic, causing failure for private VMs.
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 services — This question tests Configuring network services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable Private Google Access on subnet-b. — Private Google Access enables a VM that has only an internal IP address (no external IP) to reach Google APIs and services through the default internet gateway using Google's private network. Since subnet-b lacks this setting, VMs there cannot reach Google APIs via private IP. Enabling Private Google Access on subnet-b resolves this by allowing the VM's traffic to be routed to Google APIs without needing an external IP.
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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