TUTORIAL

How to Create Multiple Subnets in Your Network

Project Overview

EXPERIENCE LEVEL: Entry level

TIME TO COMPLETE: 30 to 45 minutes (longer if you’re brand-new to IP addressing)

ESTIMATED COST:  Free (assuming you already have access to a capable router)

Subnetting—splitting a network into smaller, isolated segments—can boost security and improve network management. In this tutorial, you’ll learn the basics of creating multiple subnets, using your home network as an example. This process is also useful in small office and remote work environments where separating traffic is critical.

Before we dive into the steps, however, let's cover a few basics. 

What is a Subnet?

A subnet is simply a smaller section of a larger network. Think of it as creating separate “neighborhoods” within the same city. Devices in one neighborhood can’t talk to devices in another without a “bridge” (a network route).

Here's an example: Your main network might be 192.168.1.xxx, where ‘xxx’ can range from 1 to 254 in most home setups. The first address is usually reserved for your router. Adding a second subnet could change the network to 192.168.2.xxx, creating a separate address space.

Why Do You Need Multiple Subnets?

While a single network might seem simpler to manage, it’s not always the most secure or efficient setup, especially as the number of connected devices in homes and offices skyrockets. 

Every laptop, phone, smart TV, printer, camera, and IoT gadget on the same network can freely “see” each other unless safeguards are in place. That means if one device is compromised (say, a vulnerable smart doorbell), it could become an entry point to your entire network.

Common reasons for setting up separate subnets include: 

• Separating IoT Devices for Security: Separating smart TVs, doorbells, and speakers from your main computers limits their access, protecting the rest of your network. 

• Isolating Work Devices from Personal Devices: If you work from home, keeping your company laptop and work-related gear on a dedicated subnet ensures business traffic isn’t mingling with your personal browsing, streaming, or gaming traffic.

• Supporting Guests or Temporary Users: A dedicated subnet for visitors lets them connect to the internet without exposing your entire network. 

• Testing and Lab Environments: If you experiment with networking configurations or run servers for learning purposes, putting them on their own subnet keeps your production devices safe.

How to Add a Second Subnet in 5 Steps 

Now, let's dig into how to set up multiple subnets. Below, we'll turn a single network into two networks. Even though those 'networks' use the same hardware, radio signals, and wires, they act as two different networks. This is the idea behind subnetting.

Step 1: Access Your Router’s Configuration Page

• Open a web browser and type your router’s IP address (often 192.168.1.1 or 192.168.0.1).

• Log in using your administrator username and password.

• Look for network or LAN settings.

Step 2: Add the Second Subnet

• In your router settings, locate the LAN or IP configuration section.

• Identify your current network (likely 192.168.1.0/24).

• Create a second network, such as 192.168.2.0/24.

• Save and apply settings.

Note: /24 means the first three octets define the network (192.168.1), leaving the last octet (xxx) for device addresses.

Step 3: Assign Devices to the New Subnet

Once your new subnet is created, you need to place devices on it so they use the new IP range. Here’s how:

• Identify Which Devices Belong on the New Subnet: Decide whether this subnet is for IoT devices, work devices, guests, or testing. Create a quick list to track what should be connected.

• Connect Devices to the Correct Network: 

• Wireless Devices: Connect them to the Wi-Fi network you’ve configured for the new subnet.

• Wired Devices: Plug them into a router port or switch port assigned to the new subnet.

• Check They’ve Received the Correct IP Address: On each device, view the network details to confirm it’s in the correct range (e.g., 192.168.2.xxx for our example). On Windows, run ipconfig; on macOS or Linux, use ifconfig or ip addr.

• Manually Assign an IP (if needed): If a device doesn’t automatically get an IP in the new range, you may need to manually set a static IP in the device’s network settings. Ensure it falls within the correct subnet range and is not already in use.

Step 4: Understand and Confirm Subnet Masks

When you’re setting up subnets, your router will ask for a subnet mask. If you don’t know what it does, it’s easy to get stuck or accidentally misconfigure your network.

A subnet mask tells a device which IP addresses are in its own subnet. Think of it as the “boundary line” for that neighborhood of devices.

• A /24 mask (255.255.255.0) means devices with the same first three octets (e.g., 192.168.1) are in the same subnet.

• Without the correct subnet mask, devices may not know who they can directly communicate with.

Here's what you'll need to do: 

• Verify Subnet mask in the Router Settings: Most home networks use 255.255.255.0 (a /24 network), but check your router’s configuration page to confirm. 

• Match the Subnet Mask to Your Intended Design: For small subnets (254 devices or fewer), use /24. If you need more devices in one subnet, use a smaller prefix (like /23 or /22).

• Be Consistent: All devices in the same subnet must use the same subnet mask, or they may not communicate properly.

Step 5: Test and Troubleshoot

After setting up your subnets, you'll want to make sure they’re working as intended. Here are a few ways to do that: 

• Test Isolation: From one subnet, use the ping command from a computer in one subnet to try to reach a device in another subnet. The ping should fail unless you've created a route between them. 

• Check Internet Access: Confirm devices in each subnet can reach the internet (if desired). If not, verify your router is set to route outbound traffic for that subnet.

• Verify Addresses: Ensure devices are receiving the correct IP address and subnet mask for their assigned subnet. On Windows, run ipconfig; on macOS or Linux, use ifconfig or ip addr.

• Fix Common Issues: If something’s off, reboot the router, then disable and re-enable the device’s network adapter to refresh its IP address. Check for overlapping IP ranges, incorrect subnet masks, or firewall rules blocking traffic.

Final Thoughts 

You’ve just created multiple subnets on your network, a powerful step toward improving network security and organization. While this was a high-level example, subnetting can get much more advanced, especially in enterprise environments. Want to learn more about networking? Our Networking Fundamentals Online Training course will teach you how to implement, maintain, troubleshoot, and fix networks. Or, check out other tutorials on our main tutorials page.