The answer is the source range mismatch, specifically that the firewall rule’s ingress source range 10.128.0.0/14 does not include the destination VM’s IP 10.132.0.3. This is because a CIDR block of /14 covers addresses from 10.128.0.0 to 10.131.255.255, so any IP outside that range, like 10.132.0.3, is blocked for return traffic even if both VMs share the same tag. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of how VPC firewall ingress rules evaluate source ranges before allowing traffic, a common trap where engineers assume tags alone guarantee connectivity. The key insight is that ingress rules filter based on the source IP of the incoming packet, not the destination VM’s tag. Memory tip: think of the CIDR as a net—if the source IP doesn’t land inside the net, the packet is dropped, regardless of tags.
PCNE Implementing a Virtual Private Cloud Practice Question
This PCNE practice question tests your understanding of implementing a virtual private cloud. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Refer to the exhibit. A VM in the default VPC with tag 'internal' and IP 10.128.1.2 is unable to communicate with another VM with IP 10.132.0.3 and tag 'internal'. What is the most likely cause?
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 source range 10.128.0.0/14 does not include 10.132.0.3.
The firewall rule allows ingress from source range 10.128.0.0/14, which covers 10.128.0.0 to 10.131.255.255. IP 10.132.0.3 is outside this range, so return traffic from VM2 to VM1 is blocked. Option A identifies this. Option B is incorrect because the rule direction is ingress, which is correct for receiving traffic. Option C is incorrect because ICMP is allowed. Option D is incorrect because priority 1000 is within the valid range and does not cause blocking.
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 rule only applies to ingress traffic.
Why it's wrong here
Ingress is the correct direction for inbound traffic; the rule is not misconfigured in direction.
Priority 1000 is normal; lower numbers are higher priority, but this does not cause blocking.
✓
The source range 10.128.0.0/14 does not include 10.132.0.3.
Why this is correct
The source range excludes 10.132.0.3, blocking return traffic.
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.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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.
Implementing a Virtual Private Cloud — This question tests Implementing a Virtual Private Cloud — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The source range 10.128.0.0/14 does not include 10.132.0.3. — The firewall rule allows ingress from source range 10.128.0.0/14, which covers 10.128.0.0 to 10.131.255.255. IP 10.132.0.3 is outside this range, so return traffic from VM2 to VM1 is blocked. Option A identifies this. Option B is incorrect because the rule direction is ingress, which is correct for receiving traffic. Option C is incorrect because ICMP is allowed. Option D is incorrect because priority 1000 is within the valid range and does not cause blocking.
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.
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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.
Question Discussion
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