- A
Use overlapping IP ranges but rely on NAT to resolve conflicts
Why wrong: NAT does not resolve routing conflicts; overlapping IPs cause asymmetric routing or loss.
- B
Use carrier-grade NAT (CGNAT) ranges for all VPCs to avoid private IP conflicts
Why wrong: CGNAT ranges are not private; they are shared and can still overlap. Best practice is to use unique RFC 1918 ranges.
- C
Use the same /16 range for all VPCs to simplify route summarization
Why wrong: Using the same range causes overlap; packets may not reach the correct destination.
- D
Allocate unique, non-overlapping IP ranges for each VPC and on-premises network
Unique ranges prevent overlap and ensure proper routing across hybrid connections.
Question 367 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.
An organization is designing IP address planning for hybrid connectivity. They have three VPCs (Prod, Dev, Test) that will be peered with each other and also connected to an on-premises network via Cloud VPN. Which practice should they follow to avoid IP address overlap?
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
✓
Allocate unique, non-overlapping IP ranges for each VPC and on-premises network
To avoid routing conflicts, each VPC and the on-premises network should use unique, non-overlapping RFC 1918 CIDR blocks. Overlap would cause routing issues and potential traffic blackholing.
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.
- ✗
Use overlapping IP ranges but rely on NAT to resolve conflicts
- ✗
Use carrier-grade NAT (CGNAT) ranges for all VPCs to avoid private IP conflicts
Why it's wrong here
CGNAT ranges are not private; they are shared and can still overlap. Best practice is to use unique RFC 1918 ranges.
- ✗
Use the same /16 range for all VPCs to simplify route summarization
Why it's wrong here
Using the same range causes overlap; packets may not reach the correct destination.
- ✓
Allocate unique, non-overlapping IP ranges for each VPC and on-premises network
Why this is correct
Unique ranges prevent overlap and ensure proper routing across hybrid connections.
Related concept
CIDR notation defines the prefix length.
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
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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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Designing, Planning, and Prototyping a GCP Network — study guide chapter
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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: Allocate unique, non-overlapping IP ranges for each VPC and on-premises network — To avoid routing conflicts, each VPC and the on-premises network should use unique, non-overlapping RFC 1918 CIDR blocks. Overlap would cause routing issues and potential traffic blackholing.
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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