PCNE Implementing network security Practice Question
A company uses VPC Service Controls to protect a managed service (e.g., BigQuery) within a service perimeter. Developers need to access the service from an on-premises network via a Cloud VPN tunnel with a specific IP address. However, access is being denied. What is the most likely cause?
⚠ Common exam trap
Google Cloud often tests the misconception that placing the VPN tunnel's project inside the service perimeter or using a specific IKE version is required, when the real issue is that VPC Service Controls evaluate the source IP of the original client, not the VPN gateway, and that IP must be explicitly allowed.
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 on-premises source IP is not included in the allowed external IP addresses list in the perimeter.
VPC Service Controls enforce access to managed services like BigQuery by restricting which source IPs can reach the service. When accessing from on-premises via Cloud VPN, the source IP seen by the service is the on-premises client's IP, not the VPN gateway's IP. If that on-premises source IP is not explicitly added to the allowed external IP addresses list in the service perimeter, access is denied, even though the VPN tunnel is established.
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 project containing the VPN tunnel is not in the same perimeter.
Why it's wrong here
The VPN tunnel's project does not need to be in the perimeter.
- ✗
The VM instances in the perimeter do not have public IP addresses.
Why it's wrong here
Private IP access is allowed within perimeter.
- ✓
The on-premises source IP is not included in the allowed external IP addresses list in the perimeter.
Why this is correct
VPC Service Controls can restrict by source IP; the on-prem IP must be allowed.
- ✗
The Cloud VPN tunnel is not using IKEv2.
Why it's wrong here
IKE version does not affect VPC Service Controls.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.