- A
The VPCs must have non-overlapping IP CIDR ranges.
Overlapping IP ranges prevent VPC peering from working.
- B
At least one VM must exist in each VPC before peering.
Why wrong: Peering can be established without any VMs.
- C
Firewall rules must allow traffic between the peered VPCs.
Even with peering, firewall rules are required for traffic to flow.
- D
The project must have a Shared VPC host project configured.
Why wrong: VPC peering does not require Shared VPC.
- E
Both VPCs must be in custom mode.
Why wrong: Auto mode VPCs can also be peered, though they have predefined subnets.
Question 133 of 1,000
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. 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.
A company has two VPCs in the same project: vpc-a (10.0.0.0/8) and vpc-b (10.0.0.0/8). They plan to peer these VPCs using VPC Network Peering. Which two prerequisites are required for the peering to work? (Choose TWO.)
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
✓
The VPCs must have non-overlapping IP CIDR ranges.
For VPC peering, the CIDR ranges must not overlap. Additionally, the 'export custom routes' and 'import custom routes' flags must be set correctly if custom routes are needed; but the basic requirement is no overlapping subnets. Also, VMs must have firewall rules allowing traffic.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 IP CIDR ranges.
Why this is correct
Overlapping IP ranges prevent VPC peering from working.
Related concept
CIDR notation defines the prefix length.
- ✗
At least one VM must exist in each VPC before peering.
Why it's wrong here
Peering can be established without any VMs.
- ✓
Firewall rules must allow traffic between the peered VPCs.
- ✗
The project must have a Shared VPC host project configured.
Why it's wrong here
VPC peering does not require Shared VPC.
- ✗
Both VPCs must be in custom mode.
Why it's wrong here
Auto mode VPCs can also be peered, though they have predefined subnets.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Visual reference
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PCNE subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this PCNE question test?
Designing, Planning, and Prototyping a GCP Network — This question tests Designing, Planning, and Prototyping a GCP Network — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The VPCs must have non-overlapping IP CIDR ranges. — For VPC peering, the CIDR ranges must not overlap. Additionally, the 'export custom routes' and 'import custom routes' flags must be set correctly if custom routes are needed; but the basic requirement is no overlapping subnets. Also, VMs must have firewall rules allowing traffic.
What should I do if I get this PCNE question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PCNE subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Last reviewed: Jul 4, 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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