The process of subnetting involves the separation of the network and subnet portion of an address
from the host identifier. This is performed by a bitwise AND operation between the IP address and
the (sub)network prefix. The result yields the network address or prefix, and the remainder is the
host identifier.
The routing prefix of an address is written in a form identical to that of the address itself. This is
called the network mask, or netmask, of the address. For example, a specification of the most-
significant 18 bits of an IPv4 address, 11111111.11111111.11000000.00000000, is written as
255.255.192.0.
