A custom-mode VPC subnet 10.0.0.0/20 is exhausted of primary internal IPs used by VMs. How do you provide more IP addresses?

The correct answer is to change the subnet CIDR from 10.0.0.0/20 to 10.0.0.0/18. This action expands the IP address range of the existing subnet, providing more primary internal IP addresses for VMs. A /18 CIDR block is larger than a /20 block, meaning it contains more available IP addresses. Adding a secondary IP range would provide additional IP addresses, but these are typically used for specific purposes like GKE pods or flexible environments, not for primary VM IPs. Changing the subnet CIDR from 10.0.0.0/20 to 10.0.0.0/22 would shrink the subnet, reducing the number of available IPs. Converting the subnet from IPv4 to IPv6 would change the IP protocol, but wouldn't directly address the exhaustion of IPv4 primary internal IPs.