GCP VPC Network Security Audit

Cloud resource audit for Google Cloud Platform VPC Network architecture, firewall posture, and connectivity. This skill evaluates provider-specific GCP networking constructs — global VPC Network design, firewall rule priority evaluation, hierarchical firewall policies, Cloud NAT egress control, Cloud Interconnect VLAN attachments, Shared VPC host/service project topology, and Cloud Router BGP sessions — not generic cloud networking advice.

Scope: auto-mode versus custom-mode VPC Networks, subnet IP ranges, firewall rules with target tags and service accounts, Cloud NAT port allocation, Cloud Interconnect and Cloud VPN connectivity, Shared VPC cross-project networking, Cloud Router dynamic routing. Out of scope: Cloud CDN, Cloud Armor WAF, load balancer URL maps, Cloud DNS. Reference references/cli-reference.md for read-only gcloud commands and references/vpc-architecture.md for the GCP global VPC model and firewall rule evaluation order.