Introduction

Every computer that communicates over the Internet is assigned a unique IP address that
identifies the device and distinguishes it from other computers on the Internet.
An IP address consists of 32 bits(8 bits equal 1 Byte) shown either as 0 "off" or 1 "on"
or as 4 octets of numbers from 0-255represented in the decimal form instead of binary.
As an example:
The IP address 168.212.226.204 in binary forms 10101000.11010100.11100010.11001100.
This is also a Class B Network;
note the first octet as being 168, which is in the Class B Network range.
It is much easier to remember decimals than binary numbers,so the use of decimal IP
addresses is much more convenient when describing them. However, the binary number
is important because that will determine which class of network the IP address
belongs to. An IP address consists of two parts, one identifying the network
and the other the node, or host. The "Class" of the address determines which
part belongs to the network address and which part belongs to the node address.
All nodes on a given network have the same network prefix but they MUST have
a unique host number.

Class A Network

Here the binary address start with 0 or as mentioned before in the "off" position,
therefore the decimal number can be anywhere from 1 to 126. The first octet
(or the first 8 bits in binary form) identifies the network and the last three octet
(or remaining 24 bits in binary) indicate the host within the network. An example of a
Class A IP address is 102.168.212.226, where "102" identifies the network and "168.212.226"
identifies the host on that network.

Class B Network

Class B binary addresses start with binary address 10 (first bit "on" second bit "off"),
therefore the decimal number can be anywhere from 128 to 191. Note that the number 127 is
skipped in the sequence; this is because it is reserved for loopback and is used for internal
testing on the local machine. The first 16 bits (the first two octets) identify the network and
the remaining 16 bits indicate the host within the network. An example of a Class B IP address is
168.212.226.204 where "168.212" identifies the network and "226.204" identifies the host on that
network.

Class C Network

Class C binary addresses start with 110 (first and second bit "on" and third "off", therefore the
decimal number can be anywhere from 192 to 223. The first 24 bits (the first three octets)
identifythe network and the remaining 8 bits indicate the host within the network.
An example of a Class C IP address is 200.168.212.226 where "200.168.212"identifies the network and "226" identifies the host on that network.

There are 2 more reserved class networks, which it is doubtful you will run across often,
they are Class D and Class E as described below.

Class D Network

Class D binary addresses start with 1110 (first, second & third bit "on" and fourth bit "off"),
therefore the decimal number can be anywhere from 224 to 239.
Class D networks are used to support multicasting.

Class E Network

Class E binary addresses start with 1111 (all four bits "on"), therefore the decimal number can
be anywhere from 240 to 255. Class E networks are used for experimentation. They have
never been documented or utilized in a standard way.
There are a number of sites and downloadable applications on the Internet for converting
binary to decimal.

Network Mask

The network mask is more properly called the subnetwork mask. However,it is generally
referred to as the network mask. It is the network mask and its implications on how IP
addresses are interpreted locally on an IP network segment that concerns us most here,
as this determines what (if any) sub-networking occurs.
The standard (sub-) network mask is all the network bits in an address set to '1' and all the host
bits set to '0'. This means that the standard network masks for the three classes of networks are:
A Class network mask: 255.0.0.0
B Class network mask: 255.255.0.0
C Class network mask: 255.255.255.0
There are two important things to remember about the network mask:
The network mask affects only the local interpretation of local IP numbers (where local means
on this particular network segment);
The network mask is not an IP number - it is used to modify how local IP numbers are
interpreted locally.



A subnet is a way of taking a single IP network address and locally splitting it up by using the
subnet mask so that this single network IP address can actually be used on several
interconnected local networks. Remember, a single IP network number can only be used
on a single network.
The important word here is locally: as far as the world outside the machines and physical
networks covered by the sub-netted IP network are concerned, nothing whatsoever has
changed - it is still just a single IP network.
This is important - sub-networking is a local configuration and is invisible to the rest of the world.

Under Construction