An explanation of subnets

In this video, TechTarget editor Jen English talks about subnets, how subnets work and why they are important in the business world.

Subnets make networking manageable.

Any information sharing between devices -- like sending a text, printing a document or downloading something from the cloud -- is a result of networking. Some networks are small -- like your home network. But enterprise networks can comprise thousands of devices and be complex to manage. That's where subnets come in.

Subnets break large networks into smaller, more manageable networks that run more efficiently and are essential in modern networking. Subnets provide more direct communication for devices in the same subnet, reducing network congestion and improving performance as a result.

Here, we'll go over the basics of how a subnet works.

Let's talk about IP addresses first. Every device on the internet -- from your phone, to a computer, to a firewall, even a cow with a tracking implant -- has an IP address, which might look like this:

When a device sends a message to another device on a different network, the message -- or data packet -- is forwarded through routers that use IP addresses to route the packet to the correct recipient. This can get inefficient and complex for large networks that don't use segmentation methods like subnets.

Think of it like a truck driver making a delivery. If it's a small town, it might not take a very long time for the driver to check every house and find the right address. But if it's a large, populated city, delivery might take a while.

Subnetting splits a large network into smaller, interconnected networks to help minimize traffic. This way, traffic doesn't flow through unnecessary routes, increasing network speeds. So, you might think of this as the truck driver looking for an address in just one neighborhood, instead of the entire city.

Back to our IP address. An IP address is typically divided into a network portion and a host portion. Network administrators use what's called a subnet mask to determine which parts of the address represent the network and the host device. The subnet mask helps pinpoint the specific destination device for a data packet.

Routers use the subnet information to find the best route between subnetworks. Here, the third section of the IP address -- dot 2 -- is used as the Subnet ID. In practice, network staff will typically refer to a subnet by just the Subnet ID, like, "Subnet 2 is having a problem today."

When a router receives a packet addressed to a host on a different subnet than the sender's -- from host A to host C, for example -- it finds the interface connected to host C's subnet and forwards the packet on that interface. This process helps maintain organized data flow across the network.

Enterprises can use subnets within their networks to separate cloud resources or departmental traffic from each other. For example, traffic from the finance department is likely under stricter privacy and security regulations. Network administrators can assign finance employees their own subnet to ensure that traffic is isolated and to better streamline monitoring and troubleshooting.

How would you rate your understanding of subnetting after watching this video? Drop your thoughts in the comments, and remember to like and subscribe, too.

Jennifer English is executive editor for TechTarget's Networking and Cloud sites. She joined TechTarget as a writer and editor after graduating from the University of New Hampshire in 2016.