Implementing GCP VPC Firewall Rules

When to Use

• When deploying new GCP workloads that require network-level access controls
• When auditing existing firewall configurations for overly permissive rules
• When implementing zero trust network segmentation within GCP VPC networks
• When responding to Security Command Center findings about open firewall rules
• When building hierarchical firewall policies across a GCP organization

Do not use for application-layer filtering (use Cloud Armor WAF), for DNS-based filtering (use Cloud DNS response policies), or for VPN/interconnect traffic filtering without understanding that VPC firewall rules apply to traffic within the VPC.

Prerequisites

• GCP project with Compute Engine API enabled
• IAM roles: roles/compute.securityAdmin for firewall management, roles/compute.networkViewer for auditing
• Organization Admin role for hierarchical firewall policies
• gcloud CLI authenticated with appropriate permissions
• VPC Flow Logs enabled on target subnets for monitoring