In simple terms, IP subnetting breaks down your network into smaller, easy-to-manage chunks. It’s just like cutting a cake into pieces so that it’s available to more people.

If you cut the cake, instead of one cake for one person, you get slices. The more slices you cut, the more people get a piece of the cake, but the slices they get are smaller.

ip subnetting

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Depending on how we cut the cake in IP addressing terms, we break the network into smaller and smaller pieces. One huge piece to one person would be a waste, so we have to determine a balance of how many slices we cut against how many people need some cake vs the size of the cake we paid for of course.

Let’s look at why we would do this.

Why Subnet a Network?

Subnetting offers several benefits:

  • Efficient Network Management: By breaking down a large network into smaller ones, you can organize and manage network traffic more effectively. This allows for better control over broadcast domains, improved security, and easier troubleshooting.
  • Performance Optimization: Subnets can help reduce network congestion and improve performance by limiting broadcast traffic and unnecessary data routing.
  • Enhanced Security: You can implement security policies specific to each subnet, creating a more secure environment by isolating sensitive data and devices.
  • Scalability: Subnetting allows for easier network expansion as it enables you to add more subnets as your organization grows.

How Subnetting Works

Subnetting involves borrowing bits from the host portion of an IP address and using them to create subnet identifiers. This is done using a subnet mask, a 32-bit value that determines which part of the IP address identifies the network and which part identifies the host.

Key Terms

  • Subnet Mask: A 32-bit number that divides an IP address into a network address and a host address.
  • Network Address: The part of an IP address that identifies the network or subnet to which a device belongs.
  • Host Address: The part of an IP address that identifies a specific device within a network or subnet.
  • CIDR Notation: A shorthand way of representing an IP address and its subnet mask. For example, 192.168.0.0/24 represents a network with the IP address 192.168.0.0 and a subnet mask of 255.255.255.0.

Example

We cover IP subnetting in great detail in our Free IP Subnetting Course, but for now, we can use a simple example.

Let’s say you have a network with the IP address 192.168.0.0/16. This represents a Class B network with a subnet mask of 255.255.0.0. You want to divide this network into four smaller subnets.

To do this, you would borrow two bits from the host portion of the IP address, leaving you with a subnet mask of 255.255.255.0 and four possible subnet addresses:

  • 192.168.0.0/24
  • 192.168.1.0/24
  • 192.168.2.0/24
  • 192.168.3.0/24

Each subnet would have its own network address and host addresses, allowing you to manage and control network traffic within each subnet separately.

Example

In the below example, a company is using the 10.0.0.0/8 network but has decided to chop it into smaller pieces in order to efficiently allocate host addresses.

Each section of the network could be managed by a different department and any section can run its own routing protocol, access lists or other security measures as well as limiting the possibility of a broadcast bringing down the network.

cidr

In Summary

IP subnetting makes sense for almost every commercial network. It offers many benefits and understanding how it works is essential if you plan to work in almost any field of IT.

So what are you waiting for?

We have a free course to help you get from beginner to IP subnetting expert. Learn IP Subnetting