An IP address is an address used to uniquely identify a device on an IP network. The address is made up of 32 binary bits which can be divisible into a network portion and host portion with the help of a subnet mask. The 32 binary bits are broken into four octets (1 octet = 8 bits). Each octet is converted to decimal and separated by a period (dot). For this reason, an IP address is said to be expressed in dotted decimal format (for example, 172.16.81.100). The value in each octet ranges from 0 to 255 decimal, or 00000000 – 11111111 binary.
Classification of IP Address
In a Class A address, the first octet is the network portion, so the Class A has a major network address of 220.127.116.11 – 127.255.255.255. Octets 2, 3, and 4 (the next 24 bits) are for the network manager to divide into subnets and hosts as he/she sees fit. Class A addresses are used for networks that have more than 65,536 hosts (actually, up to 16777214 hosts!).
In a Class B address, the first two octets are the network portion, so the Class B has a major network address of 18.104.22.168 – 22.214.171.124. Octets 3 and 4 (16 bits) are for local subnets and hosts. Class B addresses is used for networks that have between 256 and 65534 hosts.
In a Class C address, the first three octets are the network portion.
The Class C has a major network address of 192.0.0.0 – 126.96.36.199. Octet 4 (8 bits) is for local subnets and hosts – perfect for networks with less than 254 hosts.
A network mask helps you know which portion of the address identifies the network and which portion of the address identifies thenode. Class A, B, and C networks have default masks, also known as natural masks, as shown here:
Class A: 255.0.0.0 —–/8
Class B: 255.255.0.0 —/16
Class C: 255.255.255.0–/24