The correct action is to remove the host project’s Cloud NAT from subnet 10.1.0.0/24 and then create a new Cloud NAT in the service project for that same subnet. This is necessary because a fundamental constraint of Google Cloud networking is that only one NAT gateway can be associated with a given subnet—a “Cloud NAT subnet conflict” arises when you attempt to attach a second gateway. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of Shared VPC boundaries and the per-subnet NAT limitation, often appearing as a trick where engineers mistakenly try to add a second NAT or use VPC peering. A common trap is assuming that service projects can independently configure NAT on host-project subnets without removing the original gateway. Remember the one-to-one rule: one subnet, one Cloud NAT. For quick recall, think “NAT per subnet, not per project.”
PCNE Configuring network services Practice Question
This PCNE practice question tests your understanding of configuring network services. 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 service provider uses a Shared VPC with multiple service projects. The host project has a Cloud NAT configured for subnet 10.1.0.0/24 to provide outbound internet access to all service projects using that subnet. A new service project needs to use its own Cloud NAT for its VM instances in subnet 10.1.0.0/24 to meet compliance requirements. The network engineer attempts to create a Cloud NAT in the service project for that subnet but receives an error that the subnet already has a NAT gateway. What action should the engineer take to meet the compliance requirement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Remove the host project's NAT from the subnet and create a Cloud NAT in the service project for that subnet.
Option B is correct because a subnet can have only one NATgateway associated. To use a different NAT for the service project, the host project's NAT must be removed from that subnet first, then the service project's NAT can be created. Option A is impossible due to the conflict. Option C (VPC peering) would not allow the service project to have its own NAT on the same subnet. Option D (proxy instance) is not a native solution and introduces management overhead.
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.
✗
Create a new Cloud NAT in the service project for the same subnet, overwriting the existing one.
Why it's wrong here
You cannot have two NAT gateways on the same subnet; you must remove the existing one first.
✗
Use VPC peering to connect the service project to a different network that has a Cloud NAT.
Why it's wrong here
Peering does not allow the service project to control NAT on the shared subnet.
✗
Implement a proxy instance with an external IP in the service project.
Why it's wrong here
While functional, this is not a managed service and violates the requirement to use native Cloud NAT.
✓
Remove the host project's NAT from the subnet and create a Cloud NAT in the service project for that subnet.
Why this is correct
This removes the conflict and allows the service project to manage its own NAT.
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 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.
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.
Configuring network services — This question tests Configuring network services — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Remove the host project's NAT from the subnet and create a Cloud NAT in the service project for that subnet. — Option B is correct because a subnet can have only one NAT gateway associated. To use a different NAT for the service project, the host project's NAT must be removed from that subnet first, then the service project's NAT can be created. Option A is impossible due to the conflict. Option C (VPC peering) would not allow the service project to have its own NAT on the same subnet. Option D (proxy instance) is not a native solution and introduces management overhead.
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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