Subnetting is the process of dividing a larger IP network into smaller, more manageable networks called subnets. It helps organize address space, reduce broadcast domains, and make networks easier to design and operate.
Whether you are learning networking fundamentals or managing production environments, understanding subnetting is essential.
A subnet is a smaller network carved out of a larger IP range. For example, instead of using one large network for every device, you can split that space into separate subnets for servers, users, printers, or branch sites.
This improves organization, scalability, and control.
A subnet mask defines which part of an IP address represents the network and which part represents the host. For example, the subnet mask 255.255.255.0 corresponds to /24.
In a /24 network, the first 24 bits identify the network and the remaining 8 bits identify hosts.
CIDR stands for Classless Inter-Domain Routing. It is the slash notation used to describe network size, such as:
As the slash number gets larger, the subnet becomes smaller.
In traditional IPv4 subnetting, two addresses are reserved in each subnet:
That means the number of usable host addresses is usually:
Total addresses - 2
For example, a /24 has 256 total addresses, so it normally provides 254 usable IP addresses.
Let’s look at a common example:
Good subnet design helps you:
In production networks, subnetting is not just a classroom exercise. Teams often need to manage many networks across offices, customers, environments, or routing domains.
That is why an IPAM platform becomes valuable. Instead of relying on spreadsheets, teams can track subnets, IP allocations, and changes from one central place.
IPAM365 helps teams organize subnets, track IP usage, manage segmented environments, and maintain visibility as networks grow. It also supports multi-tenant environments and VRF-aware IP management for more advanced designs.
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Also read: What is IPAM? and What is VRF?