The answer is to configure Cloud Router in the host project to advertise all subnets via BGP. This is correct because in a Shared VPC architecture, the host project owns the VPC network and all its subnets, while service projects simply use those subnets. Cloud Interconnect provides the physical link, but Cloud Router with BGP dynamically advertises the host project’s subnet CIDR ranges to the on-premises router, enabling reachability to instances across every service project without needing separate configurations per project. On the Google Professional Cloud Network Engineer exam, this tests your understanding that Shared VPC centralizes routing control—a common trap is trying to configure BGP in each service project, which is unnecessary since those projects don’t own the subnets. Remember the key insight: the host project is the single source of truth for all subnets, so BGP advertising must happen there. Memory tip: “Host advertises all—service projects just fall.”
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 large organization uses Shared VPC with multiple service projects. They have an on-premises network connected via Cloud Interconnect. They want the on-premises network to be able to reach instances in all service projects. What is the recommended configuration?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure Cloud Router in the host project to advertise all subnets via BGP.
Option C is correct because in a Shared VPC architecture, the host project owns the VPC network and subnets, and Cloud Router with BGP is used to advertise the subnets from the host project to the on-premises network over Cloud Interconnect. This allows the on-premises network to reach instances in all service projects, as those instances reside in the host project's subnets. Cloud Router dynamically advertises the host project's VPC subnets via BGP, enabling seamless Layer 3 connectivity without additional per-service-project configurations.
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.
✗
Configure Cloud NAT in each service project for on-prem access.
Why it's wrong here
Cloud NAT is for outbound internet, not for on-prem connectivity.
✗
Use VPC peering between the host project and each service project.
Why it's wrong here
In Shared VPC, service projects share the host's VPC, so peering is unnecessary.
✓
Configure Cloud Router in the host project to advertise all subnets via BGP.
Why this is correct
Cloud Router in the host project automatically includes subnets from all service projects in the Shared VPC.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create separate Interconnect VLAN attachments for each service project.
Why it's wrong here
This adds complexity and cost; a single VLAN attachment to the host VPC is sufficient.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that each service project needs its own interconnect or NAT configuration, but the key is that Shared VPC centralizes networking in the host project, so a single Cloud Router with BGP advertisement in the host project provides connectivity to all service project instances.
Detailed technical explanation
How to think about this question
Cloud Router uses BGP to exchange routes with the on-premises router over the VLAN attachment. By default, Cloud Router advertises the VPC's subnets (including those used by service projects) to the on-premises network, and can also be configured to advertise custom IP ranges. The on-premises router must accept these routes and have a return path; the Cloud Router learns on-premises prefixes via BGP and installs them as dynamic routes in the VPC, enabling bidirectional communication. In a Shared VPC, all service project instances are in the host project's subnets, so a single Cloud Router in the host project is sufficient.
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.
Configuring network services — This question tests Configuring network services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure Cloud Router in the host project to advertise all subnets via BGP. — Option C is correct because in a Shared VPC architecture, the host project owns the VPC network and subnets, and Cloud Router with BGP is used to advertise the subnets from the host project to the on-premises network over Cloud Interconnect. This allows the on-premises network to reach instances in all service projects, as those instances reside in the host project's subnets. Cloud Router dynamically advertises the host project's VPC subnets via BGP, enabling seamless Layer 3 connectivity without additional per-service-project configurations.
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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