VPC (GCP)
A Virtual Private Cloud in Google Cloud is a global resource by default, unlike the regional VPC or VNet model in AWS or Azure - a single GCP VPC can span every region, with individual subnets defined per-region inside it. The default auto-mode VPC pre-creates a subnet in every region, while a custom-mode VPC starts empty until subnets are deliberately defined.
Frequently Asked Questions
Why does it matter that a GCP VPC is global while AWS/Azure networks are regional?
In AWS or Azure, connecting resources across regions means VPC peering or a transit gateway plus separate route tables per region. In GCP, one VPC's subnets can span every region under a single network, so a VM in us-central1 and one in europe-west1 can be in the same VPC and communicate over Google's private backbone without any peering setup — routing and firewall rules apply network-wide by default rather than per-region.
Auto-mode or custom-mode VPC — which should you actually use, and why does it matter?
Auto-mode pre-creates a /20 subnet in every GCP region automatically, which is convenient for a quick prototype but sprawls unwanted subnets into regions you never intend to use, complicating firewall and IP planning later. Production environments should use custom-mode and deliberately define only the regional subnets actually needed, with intentional non-overlapping CIDR ranges — auto-mode's fixed subnet sizing can't be resized to a custom range without recreating the subnet.