What are the considerations and potential challenges when migrating existing resources from a standalone VPC network to a Shared VPC setup, particularly concerning IP address management and service connectivity?
Also, given that my folder-level Editor role is granting unintended broad access, what is the recommended best practice for structuring IAM roles in a Shared VPC environment to ensure users and service accounts in service projects only have access to the specific subnets designated for them, while still maintaining necessary administrative capabilities?
Here are some considerations and challenges when migrating to Shared VPC:
IP Address Conflicts: You cannot directly migrate if your existing VPC’s IP ranges overlap with the Shared VPC’s. This often requires complex re-IPing. You’ll also need careful planning for new subnet allocations in the Shared VPC host project and managing existing static IP reservations and DNS resolution(Cloud DNS, internal DNS).
Connectivity and Firewall Rules: All network controls (firewalls, routing) shift to the Shared VPC host project, requiring consolidation and recreation of existing rules. You’ll need to re-establish any external network connections (VPNs, peering) and reconfigure load balancers and NAT gateways within the Shared VPC.
Service-Specific Migrations: Services like GKE and Cloud SQL require specific migration paths, often involving new deployments within the Shared VPC. VPC Service Controls also need to be extended.
Migration Strategy: Decide between a “lift-and-shift”(moved as-is) or a more comprehensive re-architecture. A phased migration is recommended to minimize downtime and facilitate testing.
For IAM roles in a Shared VPC use fine-grained roles scoped to specific subnets and projects, avoid broad Editor roles at folder level, and separate network admin duties to maintain security.
Recommended Practice:
Use Least Privilege Principle: Assign only the minimum roles and permissions needed for users or service accounts to perform their tasks.
Granular IAM Roles on Host Project:
In the Shared VPC host project, assign users roles like Network User (roles/compute.networkUser) scoped only to the subnets they need to use. This allows them to attach resources to those subnets without full network admin rights.
Avoid broad roles like Owner or Editor at the folder or project level unless absolutely necessary.
Delegate Administrative Tasks: Keep administrative roles (like Network Admin) limited to a small group that manages the Shared VPC host project network.
Service Project Permissions: Users in service projects should have roles scoped to their project and not host project wide permissions.
Use IAM Conditions & Groups: Use IAM Conditions or groups to further limit access based on attributes (like resource tags or subnet names).
Audit and Review Regularly: Regularly review IAM policies to detect and fix over-permissioned accounts.
You can use this guide to designate projects as Shared VPC host projects. You can also use document as a reference for roles and permission