20+ practice questions focused on Implementing network security — one of the most tested topics on the Google Professional Cloud Network Engineer exam. Each question includes a detailed explanation so you learn why the right answer is correct.
Start Implementing network security PracticeA company is using Cloud NAT for outbound internet access. They want to ensure that traffic from certain VMs always uses a specific set of NAT IPs for auditing purposes. Which three steps are necessary to achieve this? (Choose THREE.)
Explanation: To ensure specific VMs use a designated set of NAT IPs for auditing, you must first create a separate Cloud NAT gateway with the desired IPs and associate it with the VMs via subnet or tags (option D). This isolates traffic from those VMs. Next, configure VPC firewall rules to allow egress from the VMs to the internet (option E); otherwise, outbound traffic may be blocked. Finally, enable VPC Flow Logs on the subnet (option C) to capture which NAT IPs are used, providing auditability. Option A is not necessary because the default route's next hop is the internet gateway, not the NAT gateway's subnet, and Cloud NAT does not require a route pointing to its subnet. Option B is misleading: Cloud NAT uses subnet or tag associations, not IAM conditions, to control which VMs use it.
An organization uses VPC Service Controls to protect Google Cloud APIs. They need to allow a specific service account in a peripheral project to access a managed service in a protected service perimeter. What should they configure?
Explanation: VPC Service Controls uses ingress and egress rules to control data exchange between a protected service perimeter and resources outside it. To allow a specific service account in a peripheral project to access a managed service inside the perimeter, you configure an ingress rule that permits traffic from that service account to the protected service. Ingress rules define which identities and sources from outside the perimeter are allowed to access protected services. Egress rules would be used for the opposite direction (from inside to outside).
Which TWO of the following are benefits of using Cloud NAT?
Explanation: Cloud NAT provides two key benefits: it enables instances without public IPs to access the internet for outbound connections, and it automatically scales with the number of instances in a region without requiring manual provisioning or resizing. These features make it a managed and scalable solution for outbound internet access.
A company wants to restrict SSH access to a VM instance to only a specific subnet (10.0.1.0/24) and allow all traffic from the health check ranges (130.211.0.0/22 and 35.191.0.0/16) for load balancing. Which firewall rule configuration should be used for the SSH rule?
Explanation: A single firewall rule can include multiple source ranges (10.0.1.0/24, 130.211.0.0/22, 35.191.0.0/16) and apply to a target tag (ssh-allowed), allowing SSH from both the specific subnet and health check ranges. Option A is wrong because allowing SSH from 0.0.0.0/0 is too permissive. Option B is wrong because separate rules for the subnet and health check ranges would work but are not the most efficient configuration; the question asks which should be used, and a single rule is preferred. Option D is wrong because it only allows health check ranges, not the subnet.
A company is using Cloud NAT for internet access from private subnets. Security team notices that traffic from a specific VM is being blocked by external firewalls because the source IP is not the Cloud NAT IP. What is the most likely cause?
Explanation: Cloud NAT relies on the default route (0.0.0.0/0) pointing to the Cloud Router to direct traffic through the NAT gateway. If a VM has a custom route that overrides the default route (e.g., a more specific route to an external IP or a route to a different next hop), the VM's outbound traffic will bypass Cloud NAT entirely, resulting in the source IP being the VM's private IP instead of the Cloud NAT IP. This causes external firewalls to block the traffic as the source IP is not the expected NAT IP.
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Practice all Implementing network security questions1. Baseline your knowledge
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2. Review every explanation
For each question — right or wrong — read the full explanation. Understanding why an answer is correct is more valuable than knowing the answer itself.
3. Focus on exam traps
Implementing network security questions on the PCNE frequently use trap wording. Look for subtle differences in answers that test your precision, not just general knowledge.
4. Reach 80% consistently
Do repeated sessions until you score 80%+ three times in a row. Then move to mixed-mode practice to test cross-topic recall under realistic conditions.
The exact number varies per candidate. Implementing network security is tested as part of the Google Professional Cloud Network Engineer blueprint. Practicing with targeted Implementing network security questions ensures you can handle any format or difficulty that appears.
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