Sub netting is the process of breaking down of an IP network into smaller sub network is called sub net. Each sub network is a non physical description for a physical sub network.

A sub net is a segment of a network. Sub netting is a technique that allows a network administrator to divide one physical network into smaller logical network.

There are two form of sub net notation. One is standard notation and second is CIDR (Classless Internet Domain Routing) notation. Both version of notation use a base address (Network Address) to define the starting point of network such as 192.168.1.0.

In standard sub net notation, a four octet numeric value is used as with the base address.

In CIDR notation, the numbers of one in the binary version of the mask are counted from the left.

Example -192.168.1.0/24