The answer is that you need IAM permissions to establish the peering, along with non-overlapping subnet IP ranges and the requirement that the VPCs be in the same project or in different projects with appropriate shared VPC configurations. Non-overlapping CIDR blocks are critical because overlapping ranges create ambiguous routing—if both VPCs use the same subnet IP, the VPC routers cannot determine the correct destination for traffic, leading to dropped or misrouted packets. On the Google Professional Cloud Network Engineer exam, this requirement tests your understanding of how VPC routing tables and peering gateways handle traffic flow; a common trap is assuming that overlapping ranges are allowed if you use custom route advertisements, but Google Cloud strictly prohibits this. Remember the memory tip: “No overlap, no conflict—peering requires distinct IP space to keep routes distinct.”
PCNE Configuring network services Practice Question
This PCNE practice question tests your understanding of configuring network services. 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.
Which THREE of the following are requirements for VPC Network Peering?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The VPCs must have non-overlapping subnet IP ranges.
VPC Network Peering requires non-overlapping subnet IP ranges to prevent routing conflicts and ensure that traffic is correctly directed between the peered VPCs. Overlapping CIDR blocks would cause ambiguous routing, as the same IP address could exist in both VPCs, making it impossible for the VPC routers to determine the correct destination.
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 VPCs must have non-overlapping subnet IP ranges.
Why this is correct
Overlapping IP ranges cannot be peered due to routing conflicts.
Related concept
Read the scenario before looking for a memorised answer.
✗
Peering supports transitive routing.
Why it's wrong here
VPC peering is non-transitive; you cannot route through a peered VPC to another.
✓
Routes are automatically exchanged.
Why this is correct
Peering causes automatic exchange of subnet routes between the VPCs.
Related concept
Read the scenario before looking for a memorised answer.
✓
You need IAM permissions to establish the peering.
Why this is correct
The user must have compute.networks.updatePeering permission on both VPCs.
Related concept
Read the scenario before looking for a memorised answer.
✗
The VPCs must be in the same project.
Why it's wrong here
VPC peering can be across different projects and organizations.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that VPC Network Peering supports transitive routing, but the correct behavior is that peering is non-transitive and each pair must be explicitly configured.
Detailed technical explanation
How to think about this question
Under the hood, VPC Network Peering uses the Google Cloud internal infrastructure to exchange routes between the two VPCs via the Google Cloud Router, but the peering relationship is non-transitive by design — each peering connection is a point-to-point link. In a real-world scenario, if you need to connect three VPCs (A, B, C) where A peers with B and B peers with C, traffic from A to C must go through a VPN or a shared service VPC, not through B, because B does not advertise routes learned from A to C.
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: The VPCs must have non-overlapping subnet IP ranges. — VPC Network Peering requires non-overlapping subnet IP ranges to prevent routing conflicts and ensure that traffic is correctly directed between the peered VPCs. Overlapping CIDR blocks would cause ambiguous routing, as the same IP address could exist in both VPCs, making it impossible for the VPC routers to determine the correct destination.
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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