Before proceeding, you should check whether or not your IP network or networks are registered. Some registrars won't delegate a subdomain to name servers on unregistered networks, and network registries (we'll talk about them shortly) won't delegate an in-addr.arpa zone that corresponds to an unregistered network.
An IP network defines a range of IP addresses. For example, the network 15/8 is made up of all IP addresses in the range 184.108.40.206 to 220.127.116.11. The network 199.10.25/24 starts at 18.104.22.168 and ends at 22.214.171.124.