An exhausted subnet caps autoscaling with zero app-level error.
Resizing a subnet's range doesn't disrupt existing resources.
A GKE node pool's autoscaler hit a hard wall at 2 AM: its subnet's IP range was exhausted, new nodes couldn't get an address, throughput silently capped. A standing alert at 80% utilization would have surfaced this weeks earlier.
Static IPs
Decouple an address from a resource's lifecycle
Static routes
Override default routing to a specific appliance or Interconnect path