Day 5 (IP Address)

As discussed in Day 2, there are 3 IP classes. IP classes are based on first octect.
1 - 126, Class A
128 - 191, Class B
192 - 223, Class C

Class A default netmask is 8 bits, described as /8 or 255.0.0.0
Class B default netmask is 16 bits, described as /16 or 255.255.0.0
Class C default netmask is 24 bits, described as /24 or 255.255.255.0

Netmask defines the number of hosts that can be used in a given network.
Class A default netmask allows 16 million addresses in a network.
Class B default netmask allows 65536 addresses in a network.
Class C default netmask allows 256 addresses in a network.

When network addresses are used along with default netmask, they are said to be "classful addressing."

First address of the network cannot be assigned to a host. It is used to identify the network itself and it is known as "network address" or "subnet" address.

Last address of the network cannot be assigend to a host. It is used to identify all hosts in the network and it is called "broadcast address". (e.g. Ping to a broadcast address will be heard by all the hosts in the network.)

Using a netmask value greater than default value is called "Subnetting".
Using a netmask value smaller than default value is called "Supernetting".

Subnetting is used to reduce the number of hosts in a network.
Supernetting is used to increase the number of hosts in a network.

Subnetting and supernetting is called "classless addressing".