The goal is to create a landing zone facilitating private IP communication across production projects and apply organization-wide firewall rules, following best practices and minimizing operational costs.
Network Structure:Individual VPCs with Peering (A, B): While VPC Peering allows private connectivity, managing a full mesh or complex peering topology across many projects becomes operationally complex and can hit peering limits. It's not the recommended pattern for centralized connectivity in a landing zone.
Shared VPC (C, D): This is the Google-recommended practice for scenarios where resources from multiple projects need to communicate privately within a common VPC network. A central host project owns the network, and service projects use it. This simplifies network administration and connectivity.
Firewall Rules:Organization Policies (A, C): These enforce organizational constraints (e.g., disable external IPs, restrict locations) but do not define specific network firewall rules (like allowing TCP ports).
Hierarchical Firewall Policies (B, D): These allow defining firewall rules at the Organization or Folder level, which are inherited by resources in descendant projects/folders. This is the mechanism to apply consistent firewall rules (like allowing specific TCP ports) across all VMs in the organization (or a specific folder) efficiently, without managing rules in each individual VPC or project.
Combining Shared VPC for the network structure (best practice for cross-project private communication and central management) with Hierarchical Firewall Policies (for applying organization-wide firewall rules) meets all requirements efficiently and follows Google recommendations.
[References:, , Shared VPC Overview: "Shared VPC allows an organization to connect resources from multiple projects to a common Virtual Private Cloud (VPC) network..." - https://cloud.google.com/vpc/docs/shared-vpc , Hierarchical firewall policies: "Hierarchical firewall policies let you create and enforce a consistent firewall policy across your organization... They can be configured to explicitly deny traffic, or allow traffic..." - https://cloud.google.com/firewall/docs/hierarchical-firewall-policies, Google Cloud security foundations guide: Often recommends Shared VPC and centralized firewall management (using Hierarchical Firewalls or traditional firewalls with tags in the host project) as part of a secure landing zone. - (Conceptual reference, specific document may vary), , , ]
