Subnetting made easy – How to subnet a network

What is a subnet?

When we talk about subnet, we need to know about IPv4 address (Internet Protocol version 4).

An IP address is a 32-bit address, typically written as four dotted decimal octets (each octet is 8 bits). For example:
192.168.1.1

A network is defined by a subnet mask, which is also a 32-bit value. It can be written in dotted decimal format like 255.255.255.0 or in CIDR* (slash) notation like /24. The /24 means that the first 24 bits are used for the network portion, and the remaining 8 bits are used for host addresses within that network.

Let’s take an example:

• IP address: 192.168.1.1
• Subnet mask: /24 or 255.255.255.0

This means:

• The network address is 192.168.1.0
  (because the first 24 bits identify the network)
• The range of usable host addresses is from 192.168.1.1 to 192.168.1.254
• There are 256 total IPs in the subnet (2^8), but only 254 usable IP addresses because:
  • 192.168.1.0 is the network address
  • 192.168.1.255 is the broadcast address

*CIDR makes routing and IP management more flexible than the old class-based system (Class A, B, C). Instead of being forced into fixed subnet sizes, you can allocate IP blocks that exactly match your needs.