Every network device must have unique information or an address that helps to identify it in a network. The main function of network addressing is:
1. To provide unique information for the identification of a device on the network - LAN
2. It must locate a device or machine within a wider network - WAN.
This is where an IP address comes in. This is a unique address use to identify a device or machine in a network. The modern network operates on a TCP/IP settings, this is a primary protocol used to identify and locate a device on a Local area network or Internet. Every machine or device on a network must be loaded with a TCP/IP protocol. Within the TCP/IP settings, every network device has an assigned IP address which consist of four sets of 8 binary digits referred to as octets separated by a period.(.). This identifies the PC OR machine and the Subnet Mask enables the machine to be placed in a particular network.
Example of an IP address:
192.168.1.5 - decimal
Written in binary form it looks like this:
220.127.116.11.0.0.0.0 18.104.22.168.22.214.171.124 0.0.0.0.0.0.0.1 0.0.0.0.0.1.0.1
The first part of the address identifies the network ID, while the other parts shows the host ID
192.168.1.5 Where 192.168.1 - Network ID, 5 - Host ID.
However, IP addresses are divided into classes. The table below summarizes the classes and Subnet Mask:
Class - Address Range - Subnet Mask
A - 1- 126 - 255.0.0.0
B - 129 - 191 - 255.255.0.0
C - 192 - 223 - 255.255.255.0
Using the above table lets try and clarify it further
The Class A networks use the first octet to identify the network address, while the remaining three octets is use to identify the host or machine.
The Class B networks use the first two octets to identify the network, while the last two identifies the host or machine
The Class C networks use the first three octets as network ID and the last octet as host or machine ID.
The subnet mask is the value use to show the part of an IP address that signifies the network ID. Simply said, the subnet mask differentiates the network portion to the host portion.
Take for example, Class C IP 192.168.10.25 with a subnet mask 255.255.255.0 is distinguished as follows:
192.168.10 - Network address
25 - Host address
Class B 172.17.20.10 with a subnet mask 255.255.0.0 is separated as follows
20.10 - Host
Initially, addressing network devices in this 'Classful' way results to wasting of usable IP addresses, the TCP/IP engineers came up with several ways to cub this wastage by the use of Subnetting, Variable Length Subnet Masking (VLSM), Classless InterDomain Routing (CIDR), and Network Address Translation (NAT)