Question

You are designing a custom-mode VPC that must host several regional subnets. Each subnet needs a primary range for VM instances plus a secondary range that a future GKE VPC-native cluster will use for Pods. You must reserve a contiguous, private, non-overlapping addressing plan across three regions and leave headroom for growth without renumbering. Which IP addressing design best satisfies these requirements?

Accepted Answer

Allocate one large RFC 1918 supernet (e.g., 10.0.0.0/9), carve a distinct /16 per region, and within each region assign a smaller primary CIDR and a separate non-overlapping secondary CIDR for Pods.

Answer

Use auto-mode subnets so Google automatically assigns 10.128.0.0/9 ranges per region, then add secondary ranges that overlap the auto-assigned primary ranges to conserve space.

Answer

Assign the same primary and secondary CIDR blocks in all three regions to simplify management, since subnets in different regions can reuse identical ranges.

Answer

Place all VMs and all Pods in a single flat /24 primary range per region and rely on NAT to translate Pod addresses onto the VM range.