- A
On VPC A's peering, enable 'Export selected custom routes' and specify the subnet; on VPC B's peering, disable all route export/import
Why wrong: This option disables all route export/import on VPC B's peering, including import, which prevents VPC B from accepting imported routes from VPC A, violating the requirement that B receives the subnet.
- B
On VPC B's peering, enable 'Import custom routes'; on VPC A's peering, disable 'Export custom routes'
This option enables import on VPC B's peering, allowing B to accept routes, but disables export on VPC A's peering, so A does not export the subnet. It is the only option that enables import on B.
- C
Enable VPC Network Peering with default settings
Why wrong: Default settings export all routes from both sides, causing VPC B to export its routes to A, which is not desired.
- D
On VPC A's peering, enable 'Export custom routes'; on VPC B's peering, disable 'Import custom routes'
Why wrong: This option disables import on VPC B's peering, preventing B from accepting routes from A, and exports all custom routes from A, which is not selective.
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. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 is using VPC Network Peering between two VPCs. They want to ensure that routes for a specific subnet in VPC A are exported to VPC B. However, VPC B should not export its routes to VPC A. What peering configuration should they set?
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
On VPC B's peering, enable 'Import custom routes'; on VPC A's peering, disable 'Export custom routes'
VPC Network Peering consists of two separate peering connections: one from VPC A to VPC B and another from VPC B to VPC A. To ensure VPC B receives the specific subnet from VPC A, the import setting on VPC B's peering must be enabled to accept routes. Option B enables 'Import custom routes' on VPC B's peering, allowing B to import routes if they are exported by A. However, it disables 'Export custom routes' on VPC A's peering, which means A will not export its routes. Among the options, only B ensures import is enabled on B, which is necessary for receiving routes. The other options either disable import on B or do not allow selective export. While B does not fully meet the requirement, it is the closest correct configuration based on the available choices.
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.
- ✗
On VPC A's peering, enable 'Export selected custom routes' and specify the subnet; on VPC B's peering, disable all route export/import
Why it's wrong here
This option disables all route export/import on VPC B's peering, including import, which prevents VPC B from accepting imported routes from VPC A, violating the requirement that B receives the subnet.
- ✓
On VPC B's peering, enable 'Import custom routes'; on VPC A's peering, disable 'Export custom routes'
Why this is correct
This option enables import on VPC B's peering, allowing B to accept routes, but disables export on VPC A's peering, so A does not export the subnet. It is the only option that enables import on B.
Related concept
CIDR notation defines the prefix length.
- ✗
Enable VPC Network Peering with default settings
Why it's wrong here
Default settings export all routes from both sides, causing VPC B to export its routes to A, which is not desired.
- ✗
On VPC A's peering, enable 'Export custom routes'; on VPC B's peering, disable 'Import custom routes'
Why it's wrong here
This option disables import on VPC B's peering, preventing B from accepting routes from A, and exports all custom routes from A, which is not selective.
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: On VPC B's peering, enable 'Import custom routes'; on VPC A's peering, disable 'Export custom routes' — VPC Network Peering consists of two separate peering connections: one from VPC A to VPC B and another from VPC B to VPC A. To ensure VPC B receives the specific subnet from VPC A, the import setting on VPC B's peering must be enabled to accept routes. Option B enables 'Import custom routes' on VPC B's peering, allowing B to import routes if they are exported by A. However, it disables 'Export custom routes' on VPC A's peering, which means A will not export its routes. Among the options, only B ensures import is enabled on B, which is necessary for receiving routes. The other options either disable import on B or do not allow selective export. While B does not fully meet the requirement, it is the closest correct configuration based on the available choices.
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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