The key to understanding IP is knowing what a routing table looks
IP addresses are 32 bit numbers and are represented in a dotted
Each decimal number represents eight bits of binary data, and
therefore can have a decimal value between 0 and 255:
It is the value of the first number of the IP address that determines
the class to which a given IP address belongs. IP addresses most
commonly are class A, B, or C.
127.0.0.0 is a class A network, but is reserved for use as a
loopback address (typically 127.0.0.1).
The 0.0.0.0 network is reserved for use as the default route.
Class D addresses are used by groups of hosts or routers that
share common characteristics.
Class D addresses are used for multi-cast applications.
Class E addresses exist (240-248) but are reserved for future
RFC 790 - Assigned numbers