October 7, 2019

What Does IPv4 Subnetting Mean?

Subnetting refers to a defined course of action that takes a network and splits it into smaller ones, which are called subnets. The method is generally used to make more public IPv4 addresses available as well as to create segment networks, which makes it easy to manage the network and improves security.

The subnetting process can be easily understood if you were acquainted with how the binary structure of IP addresses and their decimals work. As an IPv4 address is characteristically a 32-bit number, they are categorized into 4 x 8-bit numbers to make the IP addresses simpler. These 8-bit numbers, known as octets, are separated using a decimal point and range within 0 to 255.

The highest number here is kept 255 because IP addresses are binary. While a binary number is represented in 0s and 1s, it symbolizes the numbers 128:64:32:16:8:4:2:1 in a network; note that 1 activates the digit in its position. For instance, a binary number 1000001 would denote [128]000000[1], which would add up to 129. Therefore, if all the numbers were activated, it would be 128+64+32+16+8+4+2+1 = 255. The biggest possible IP address is 255.255.255.255, which would look like 11111111.11111111.11111111.11111111 in binary.

In the early days when the internet was starting to flourish, most organizations issued all the IP addresses possible until they almost ran out. Fortunately, the subnetting process was discovered by IPv4 address designers, which simplified the task of assigning IP addresses for large enterprises.

There are two main parts of any IP address – the network and the host. Subnetting typically defines the numerical figure of bits that are used in the network part of the IP address, while assigning different hosts. It can also be represented using a slash, which is called CIDR notation. For instance, if a subnet is represented with /8, it means that it is using 8 bits out of the total 32 bits.

Note that every host would have the same first three octets in a network. So even if there were 100 subnets created, they all would have the same first three digits to denote their network. However, subnetting would allow the network administrator to assign any number from 1 to 255 in the last part of the IP address. For instance, an IP address with /24 subnetting would have the subnet mask as 255.255.255.0, which would be 11111111.11111111.11111111.00000000 in binary. Here, 254 subnets can be assigned within the same network.