The answer is firewall rules allowing traffic to the restricted VIP IP range 199.36.153.4/30, a Cloud VPN tunnel or Dedicated Interconnect connection, and on-premises DNS resolution for private.googleapis.com. This trio is required because on-premises hosts must resolve Google APIs to the restricted VIP, then route that traffic over the VPN or Interconnect, while firewall rules at the Google Cloud perimeter explicitly permit only authorized source IPs to reach that VIP—without them, the traffic is dropped. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding that Private Google Access for on-premises hosts is not automatic; a common trap is assuming Cloud NAT or VPC firewall rules alone suffice, when in fact the restricted VIP’s perimeter firewall is the gatekeeper. Remember the mnemonic “Route, Resolve, and Restrict”: a route via VPN/Interconnect, DNS resolution to the restricted VIP, and a firewall rule restricting access to that VIP.
PCNE Implementing network security Practice Question
This PCNE practice question tests your understanding of implementing network security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Which THREE of the following are required to use Private Google Access for on-premises hosts through a Cloud VPN or Interconnect? (Choose THREE)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Firewall rules allowing traffic from on-premises to the restricted VIP IP range.
Private Google Access for on-premises hosts requires firewall rules that allow traffic from on-premises to the restricted VIP IP range (199.36.153.4/30). This is necessary because on-premises hosts must be able to reach the restricted Google APIs VIP over the VPN or Interconnect, and firewall rules control which source IPs can access that VIP. Without these rules, traffic from on-premises would be blocked at the Google Cloud perimeter.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Firewall rules allowing traffic from on-premises to the restricted VIP IP range.
Why this is correct
Traffic must be allowed to reach the VIP.
Related concept
Read the scenario before looking for a memorised answer.
✗
VPC Flow Logs enabled on the VPC.
Why it's wrong here
Flow logs are not required for functionality.
✓
Configuring DNS on-premises to resolve Google API hostnames to the restricted Google APIs IP address (199.36.153.4/30).
Read the scenario before looking for a memorised answer.
✓
A Cloud VPN tunnel or Dedicated Interconnect connection to Google Cloud.
Why this is correct
A connection is needed for on-prem to reach GCP.
Related concept
Read the scenario before looking for a memorised answer.
✗
Cloud NAT configured for the on-premises subnet.
Why it's wrong here
Cloud NAT is for VMs without public IPs, not for on-premises.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that Cloud NAT is required for on-premises traffic, but Cloud NAT is only for Google Cloud VMs without external IPs, not for on-premises hosts using Private Google Access.
Detailed technical explanation
How to think about this question
Private Google Access for on-premises relies on the restricted.googleapis.com VIP (199.36.153.4/30), which is a special IP range that only accepts traffic from authorized sources (e.g., VPC networks or on-premises via VPN/Interconnect). DNS resolution on-premises must map Google API hostnames to this VIP, and the Cloud VPN or Interconnect provides the Layer 3 path. Under the hood, Google Cloud uses BGP to advertise the restricted VIP over the interconnect, and firewall rules act as a control plane to permit the traffic.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Implementing network security — This question tests Implementing network security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Firewall rules allowing traffic from on-premises to the restricted VIP IP range. — Private Google Access for on-premises hosts requires firewall rules that allow traffic from on-premises to the restricted VIP IP range (199.36.153.4/30). This is necessary because on-premises hosts must be able to reach the restricted Google APIs VIP over the VPN or Interconnect, and firewall rules control which source IPs can access that VIP. Without these rules, traffic from on-premises would be blocked at the Google Cloud perimeter.
What should I do if I get this PCNE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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