- A
Internal load balancers are regional; clients must be in the same region as the load balancer when using VPC peering.
Internal TCP/UDP LBs are regional and only accept connections from VPCs in the same region via peering.
- B
The VPC peering connection does not propagate routes for the load balancer IP.
Why wrong: VPC peering exports all subnet routes, including the internal IP address of the load balancer.
- C
The backend instances are unhealthy and the load balancer is not serving traffic.
Why wrong: The stem does not mention health check issues, and even if backends were unhealthy, the load balancer would still accept connections and return errors.
- D
Firewall rules in VPC-B are not allowing egress to the load balancer IP.
Why wrong: Egress firewall rules are permissive by default in VPC, and the engineer verified they allow traffic.
Quick Answer
The answer is that the internal load balancer is not accessible over VPC peering because internal load balancers are regional resources, and clients must reside in the same region as the load balancer when using VPC peering. This is the most likely reason for the failure: even with correct firewall rules, an internal TCP load balancer in us-central1, for example, will not accept traffic from instances in VPC-B located in us-west1 over a VPC peering connection. The Google Professional Cloud Network Engineer exam tests this specific regional restriction to ensure you understand that internal load balancers lack cross-region support via peering—unlike external load balancers, which can use global access. A common trap is assuming VPC peering makes all resources globally reachable, but internal LBs remain region-bound unless you use a proxy or Network Connectivity Center. Memory tip: “Internal is regional, peering is regional—same region or no connection.”
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.
A company has two VPC networks (VPC-A and VPC-B) in the same project. They are connected via VPC peering. VPC-A contains an internal TCP load balancer with IP 10.1.2.3 serving on port 80. VPC-B needs to access this load balancer. The network engineer has verified that the firewall rules allow traffic from VPC-B to the load balancer's IP and port. However, instances in VPC-B cannot connect to 10.1.2.3:80. What is the most likely reason for this failure?
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 choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Internal load balancers are regional; clients must be in the same region as the load balancer when using VPC peering.
Option C is correct: Internal TCP/UDP load balancers are regional and only accept traffic from clients in the same region when using VPC peering. The load balancer is in a specific region (e.g., us-central1), but if VPC-B's instances are in a different region (e.g., us-west1), they will not be able to reach the internal LB via peering unless the LB has global access enabled (which is only available for external LBs). Option A is incorrect because firewall rules are already verified. Option B is irrelevant; VPC peering does not insert a default route for load balancer IPs. Option D is incorrect because health checks are for the load balancer to backends, not client connectivity.
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.
- ✓
Internal load balancers are regional; clients must be in the same region as the load balancer when using VPC peering.
- ✗
The VPC peering connection does not propagate routes for the load balancer IP.
Why it's wrong here
VPC peering exports all subnet routes, including the internal IP address of the load balancer.
- ✗
The backend instances are unhealthy and the load balancer is not serving traffic.
Why it's wrong here
The stem does not mention health check issues, and even if backends were unhealthy, the load balancer would still accept connections and return errors.
- ✗
Firewall rules in VPC-B are not allowing egress to the load balancer IP.
Why it's wrong here
Egress firewall rules are permissive by default in VPC, and the engineer verified they allow traffic.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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 PCNE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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Configuring network services — study guide chapter
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FAQ
Questions learners often ask
What does this PCNE question test?
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: Internal load balancers are regional; clients must be in the same region as the load balancer when using VPC peering. — Option C is correct: Internal TCP/UDP load balancers are regional and only accept traffic from clients in the same region when using VPC peering. The load balancer is in a specific region (e.g., us-central1), but if VPC-B's instances are in a different region (e.g., us-west1), they will not be able to reach the internal LB via peering unless the LB has global access enabled (which is only available for external LBs). Option A is incorrect because firewall rules are already verified. Option B is irrelevant; VPC peering does not insert a default route for load balancer IPs. Option D is incorrect because health checks are for the load balancer to backends, not client connectivity.
What should I do if I get this PCNE question wrong?
Identify which PCNE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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.
About these practice questions
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Last reviewed: Jun 24, 2026
This PCNE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCNE exam.
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