- A
The subnet routes are exported from VPC-B to VPC-A.
Correct. Subnet routes must be exported from VPC-B to VPC-A for peering to work. If not exported, instances in VPC-A cannot reach VPC-B.
- B
The BGP session status on the Cloud Router.
Why wrong: Incorrect. BGP sessions on Cloud Router are used for hybrid connectivity (VPN/Direct Connect), not for VPC peering.
- C
The MTU size of the instances.
Why wrong: Incorrect. MTU mismatch may cause performance issues but not complete connectivity failure.
- D
The route tables for the peered network.
Why wrong: Incorrect. Route tables in VPC-A do not automatically include routes to VPC-B unless subnet routes are exported from VPC-B. The issue is export, not the route table itself.
Question 22 of 1,000
VPC Peering Route Export — Troubleshooting Connectivity
This PCNE practice question tests your understanding of implementing a virtual private cloud. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: vPC Network Peering. 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 engineer has set up VPC Network Peering between VPC-A and VPC-B. Both VPCs have non-overlapping CIDR ranges. The peering state is ACTIVE. However, instances in VPC-A cannot reach instances in VPC-B. The engineer verified that firewall rules allow the traffic. What should the engineer check next?
Quick Answer
The correct step is to verify that subnet routes are exported from VPC-B to VPC-A, because VPC Network Peering requires explicit route export for connectivity, even when the peering state shows ACTIVE. While firewall rules may permit traffic, without the proper export of subnet routes from the peered VPC, the source VPC has no path to the destination—the routes simply do not appear in its route table. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding that default route export can be disabled, often through settings like exportSubnetRoutesWithPublicIp, and that an ACTIVE peering state only confirms the control plane is up, not that routes are shared. A common trap is assuming ACTIVE peering equals full connectivity, or misdiagnosing MTU or BGP issues. Remember the memory tip: "Peering is active, but routes are missing—check the export, not the handshake."
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 subnet routes are exported from VPC-B to VPC-A.
Option A is correct because VPC Network Peering requires that subnet routes be exported from the peered VPC. By default, subnet routes are automatically exported, but if the peering configuration was modified (e.g., exportSubnetRoutesWithPublicIp set to false), routes may not be exported. The engineer should verify that VPC-B exports its subnet routes to VPC-A. Option B is incorrect because BGP is not used in VPC peering; Cloud Router is used for Cloud VPN or Dedicated Interconnect, not peering. Option C is incorrect because MTU mismatch is unlikely to cause complete lack of connectivity. Option D is incorrect because the route tables themselves are not the issue; the missing routes are due to export settings, not the presence of route tables.
Key principle: VPC Network Peering
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 subnet routes are exported from VPC-B to VPC-A.
Why this is correct
Correct. Subnet routes must be exported from VPC-B to VPC-A for peering to work. If not exported, instances in VPC-A cannot reach VPC-B.
Related concept
VPC Network Peering
- ✗
The BGP session status on the Cloud Router.
- ✗
The MTU size of the instances.
Why it's wrong here
Incorrect. MTU mismatch may cause performance issues but not complete connectivity failure.
- ✗
The route tables for the peered network.
Why it's wrong here
Incorrect. Route tables in VPC-A do not automatically include routes to VPC-B unless subnet routes are exported from VPC-B. The issue is export, not the route table itself.
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
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- VPC Network Peering
- Route Export
- Firewall Rules
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
VPC Network Peering
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 vPC Network Peering, then practise related PCNE questions on the same topic to reinforce the concept.
- →
Implementing a Virtual Private Cloud — study guide chapter
Learn the concepts, then practise the questions
- →
Implementing a Virtual Private Cloud practice questions
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FAQ
Questions learners often ask
What does this PCNE question test?
Implementing a Virtual Private Cloud — This question tests Implementing a Virtual Private Cloud — VPC Network Peering.
What is the correct answer to this question?
The correct answer is: The subnet routes are exported from VPC-B to VPC-A. — Option A is correct because VPC Network Peering requires that subnet routes be exported from the peered VPC. By default, subnet routes are automatically exported, but if the peering configuration was modified (e.g., exportSubnetRoutesWithPublicIp set to false), routes may not be exported. The engineer should verify that VPC-B exports its subnet routes to VPC-A. Option B is incorrect because BGP is not used in VPC peering; Cloud Router is used for Cloud VPN or Dedicated Interconnect, not peering. Option C is incorrect because MTU mismatch is unlikely to cause complete lack of connectivity. Option D is incorrect because the route tables themselves are not the issue; the missing routes are due to export settings, not the presence of route tables.
What should I do if I get this PCNE question wrong?
Review vPC Network Peering, then practise related PCNE questions on the same topic to reinforce the concept.
What is the key concept behind this question?
VPC Network Peering
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Last reviewed: Jun 24, 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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