A large organization wants to centralize network administration and security policies across all its GCP projects (Dev, Test, Prod). All VMs need to…

Shared VPC is the Google Cloud feature designed specifically for this use case. It allows an organization to designate a central "Host Project" to own and manage network resources like VPCs, subnets, and firewall rules. Other projects, such as Dev, Test, and Prod, are designated as "Service Projects." These Service Projects can then use the subnets from the Host Project, effectively sharing the same network infrastructure and security policies while maintaining separate billing, IAM, and resource ownership. This model centralizes network administration and security, fulfilling all the requirements of the question.

A. Using a single project breaks the required organizational separation for Dev, Test, and Prod, which is a critical anti-pattern for managing IAM, quotas, and billing in a large organization.

C. VPC Network Peering connects distinct, non-overlapping VPC networks. It does not centralize administration or allow projects to share the same subnets and firewall rules; each project would still manage its own network.

D. Cloud Router with BGP is used for dynamic routing between a VPC and an external network (like on-premises) via Cloud VPN or Interconnect, not for centralizing network management across GCP projects.

1. Google Cloud Documentation, "Shared VPC overview": "Shared VPC allows an organization to connect resources from multiple projects to a common Virtual Private Cloud (VPC) network... With Shared VPC, you designate a project as a host project and attach one or more other service projects to it. The VPC networks in the host project are called Shared VPC networks. Eligible resources from service projects can use subnets in the Shared VPC network." This document explicitly describes the architecture in option B as the solution for centralized control.

2. Google Cloud Documentation, "VPC Network Peering overview": "VPC Network Peering lets you connect two VPC networks so that workloads in different VPC networks can communicate internally... The VPC networks can be in the same project, different projects, or projects in different organizations." This highlights that peering connects different networks, which contradicts the requirement to share the same subnet ranges.

3. Google Cloud Architecture Framework, "Network design and security": In the section on network topology, Shared VPC is presented as a primary model for organizations that require centralized control over network resources. It states, "Shared VPC lets you maintain centralized control over network resources like subnets, routes, and firewalls in a host project." This reinforces Shared VPC as the best practice for the scenario.