Create a new network
You can create IP address range groups to control access to the services you provide. These ranges can be ones you control on your private network, or they can be any publicly accessible IP address range.
Give the network a name.
You can name your ranges anything you choose, except Private networks or Only this Mac.
Enter the starting IP address and the ending IP address.
You can put an address range in CIDR notation (for example, 10.0.0.1/16) in the Starting IP Address field, then the ending address will automatically be entered.