The answer is specifying a subnet in the same region as the backend instances. This is required because an internal load balancer (ILB) in GCP must have its internal IP address allocated from a subnet within the same VPC and region as the backend instances, and the regional forwarding rule references that subnet to enable internal-only routing. Without this subnet specification, the load balancer cannot be provisioned as an internal resource, as the subnet defines the IP range for private traffic distribution. On the Google Professional Cloud Network Engineer exam, this tests your understanding of the ILB’s regional scope versus a global external load balancer; a common trap is assuming any subnet in the VPC works, but the subnet must match the backend’s region. Remember the memory tip: “Internal means regional subnet—same region as the backend, or the traffic won’t send.”
PCNE Practice Question: Designing, planning, and prototyping a GCP network
This PCNE practice question tests your understanding of designing, planning, and prototyping a gcp network. 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 is deploying an internal load balancer (ILB) in a VPC to distribute traffic among backend instances in a managed instance group. The ILB should only be accessible from within the VPC. Which of the following is a required step when configuring the ILB?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Specify a subnet in the same region as the backend instances.
An internal load balancer (ILB) in GCP requires a regional forwarding rule that routes traffic to backend instances within the same VPC. Specifying a subnet in the same region as the backend instances is mandatory because the ILB's internal IP address is allocated from that subnet, and the forwarding rule must reference a subnet to enable internal-only routing. Without a subnet, the ILB cannot be provisioned as an internal load balancer.
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.
✗
Assign a static external IP address to the forwarding rule.
Why it's wrong here
ILB uses an internal IP address.
✗
Upload an SSL certificate to the load balancer.
Why it's wrong here
ILB does not terminate SSL; that's for external HTTPS load balancers.
✓
Specify a subnet in the same region as the backend instances.
Why this is correct
The ILB's IP is allocated from a subnet in the same region.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create a Cloud NAT gateway for the backend instances.
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that an internal load balancer requires an external IP or SSL termination, but the key requirement is specifying a subnet in the same region as the backends for internal IP allocation.
Detailed technical explanation
How to think about this question
Under the hood, the ILB forwarding rule uses an internal IP address from the specified subnet, and GCP's Andromeda software-defined networking implements VXLAN-based encapsulation to forward traffic to backend instances in the same VPC. A common subtlety is that the subnet must be in the same region as the backend instances, but the forwarding rule's internal IP can be in any subnet within that region, as long as it is not in a subnet that overlaps with on-premises networks via VPN. In real-world scenarios, misconfiguring the subnet region leads to a 'subnet not found' error during forwarding rule creation.
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.
Designing, planning, and prototyping a GCP network — This question tests Designing, planning, and prototyping a GCP network — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Specify a subnet in the same region as the backend instances. — An internal load balancer (ILB) in GCP requires a regional forwarding rule that routes traffic to backend instances within the same VPC. Specifying a subnet in the same region as the backend instances is mandatory because the ILB's internal IP address is allocated from that subnet, and the forwarding rule must reference a subnet to enable internal-only routing. Without a subnet, the ILB cannot be provisioned as an internal load balancer.
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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