How Many IPs Are in a /24 Subnet?

There are 256 IP addresses in a /24 subnet. However, not all 256 addresses can be used by devices on the network. The first and last addresses are reserved for network functions, leaving only 254 IP addresses available.

This article breaks down the mathematics behind a /24 subnet, its real-world applications, and how to identify and verify this subnet size in network settings.

Table of Contents

1. Understanding The /24 Subnet Notation
   • How We Calculate the IP Address Breakdown
   • Key Benefits
2. Why The Need for Reserved Addresses?
   • The Network Address
   • The Broadcast Address
3. When is The /24 Subnet Used?
   • Home Networks
   • Small to Medium Sized LANs
   • Network Segmentation in Larger Companies
   • Virtual Networks and Test Environments
4. How to Identify and Verify a /24 Subnet
   • On Windows
   • On Linux and macOS
   • On Routers and Networking Devices
5. What About Other Subnet Sizes?
   • /16 Subnet
   • /20 Subnet
   • /30 Subnet
   • /28 Subnet
6. Final Thoughts

1. Understanding The /24 Subnet Notation

IP addresses (specifically IPv4) contain 32 bits. When a subnet is specified, we can identify how many devices the subnet supports. In the case of /24, the first 24 bits are reserved for identifying the network, leaving the remaining 8 bits for devices within that network.

The /24 subnet is common because it provides a manageable number of IP addresses. Remember, the number only indicates the maximum number of devices supported. Therefore, a /24 is ideal for most small to medium businesses.

a. How We Calculate the IP Address Breakdown

To calculate the total number of possible IPs, we focus on those 8 remaining bits. Each bit can be a 0 or a 1, giving us two possible values per bit. With 8 bits available, we calculate the total possible IPs by raising 2 to the power of 8, which is 256.

This means a /24 subnet has 256 total IP addresses. Here’s how these addresses are broken down:

• Total IP Addresses in a /24 Subnet: 256
• Reserved Addresses:
  • Network Address: The first IP in the subnet, which identifies the subnet itself.
  • Broadcast Address: The last IP in the subnet, used for sending messages to all devices within the subnet.

Since individual devices cannot use these two addresses, the number of usable IP addresses in a /24 subnet is 254 (256 total – 2 reserved).

b. Key Benefits

• Manageability: Only has a moderate number of IPs to handle and troubleshoot.
• Scalability: Reduces the need for frequent subnet reconfiguration.
• Isolation and Security: Allows for logical separation of network segments.
• Reduced Broadcast Traffic: Compared to larger subnets, a /24 subnet keeps broadcast traffic to a minimum.

2. Why The Need for Reserved Addresses?

Although we still have 254 usable IP addresses, those on the fringe of that number of devices might get frustrated and ask, “But why?” Unfortunately, they play a vital role in the subnet and cannot be reallocated for device use.

a . The Network Address

The network address is the very first IP address in the subnet. In a /24 subnet, this address is represented by setting all host bits to 0. This address identifies the subnet and is used by routers and networking devices to locate and reference the entire subnet. 

For example, in a 192.168.1.0/24 subnet, the network address is 192.168.1.0.

Don’t mistake the role of the network address as a simple one. “Network identification” is an oversimplification of what this address does. It is also used for things like:

• Efficient Routing
• Network Boundary Definition
• Broadcast and Host Address Management
• Simplified Network Configuration and Troubleshooting

b. The Broadcast Address

The broadcast address is the last IP address in the subnet, created by setting all host bits to 1. In the example above, we used a 192.168.1.0/24 subnet. Therefore, the broadcast address would be 192.168.1.255. 

This address is used to send messages to all devices within the subnet. When a device sends data to the broadcast address, all devices in the subnet receive the data, which can be useful for announcements or network-wide messages.

For example, the broadcast address may send:

• Address Resolution Protocol Requests
• Dynamic Host Configuration Protocol Discovery
• Routing and Network Announcements 
• Network Management and Monitoring
• Wake-on-LAN

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3. When is The /24 Subnet Used?

Earlier, I mentioned that the /24 subnet is most commonly used. The main reason for this is the massive number of home networks today. Practically every household is a network in its own right.

Let’s consider the overall use cases for /24 subnets:

a. Home Networks

Almost all of us today have a broadband router at home. This router manages your home network and handles the connectivity of every other device at the location, such as IoT devices, computers, smart TVs, and smartphones.

A/24 subnet is most often used since it is the smallest and can scale sufficiently for almost any home size—well, unless you pack your home with more than 254 devices.

b. Small to Medium-Sized LANs

In small to medium-sized offices, /24 subnets are often used for local area networks (LANs). With 254 available IP addresses, a /24 subnet can comfortably support various devices, including employee workstations, printers, IP phones, and wireless access points. 

This subnet size allows for efficient device organization and minimal IP address waste. It’s also more simple for smaller IT departments to manage effectively.

c. Network Segmentation in Larger Companies

Large organizations use network segmentation to improve performance and security. IT teams can simplify traffic management and enhance security by assigning a /24 subnet to different parts of the network. 

For example, the company may segregate networks between individual floors of a building, different departments, or guest networks. Each will get its own /24 subnet, which functions as parts of a larger network.

d. Virtual Networks and Test Environments

A/24 subnet provides a manageable address space for IT teams and developers setting up virtual networks or test environments. These networks often need flexibility to test various devices, services, or applications, and a /24 subnet’s 254 IPs can support this setup.

4. How to Identify and Verify a /24 Subnet

A /24 subnet is commonly recognized by its subnet mask, 255.255.255.0. This subnet mask corresponds to the 24 bits allocated to the network portion of the IP address. You can check this subnet mask relatively easily.

a. On Windows

• Launch the Command Prompt to view network configurations.
• Type ipconfig and press Enter. Look for the line labeled “Subnet Mask” under the network adapter in use.
• If the subnet mask shows 255.255.255.0, it’s a /24 subnet.

b. On Linux and macOS

For those with Linux systems, use Terminal and type ifconfig (or ip addr show for newer versions) to see network details.

On macOS:

• Open Terminal and enter ifconfig.
• Locate the active network interface (usually eth0 or en0). The subnet mask will be displayed in hexadecimal form (0xffffff00 for 255.255.255.0).
• This notation indicates a /24 subnet, as it corresponds to 24 bits allocated to the network.

c. On Routers and Network Devices

Many routers and networking devices allow you to configure or view subnet settings through a web interface. Log into your router’s settings page and navigate to the network or LAN configuration section.

Here, you should see the subnet mask displayed alongside IP settings, often defaulting to 255.255.255.0 for home and small business routers.

5. What About Other Subnet Sizes?

While a /24 subnet is a popular choice, it’s helpful to understand how it compares to other subnet sizes. After all, you may one day design a network that requires more IP addresses.

Here’s a look at how a /24 subnet stacks up against other common subnet sizes:

a. /16 Subnet

A /16 subnet offers significantly more IPs than a /24, allowing up to 65,534 devices. However, managing this many devices in a single subnet can lead to higher broadcast traffic, which may impact network performance.

• Total IPs: 65,536
• Usable IPs: 65,534
• Subnet Mask: 255.255.0.0

b. /20 Subnet

A /20 subnet supports 4,094 usable IP addresses, making it a good choice for growing organizations. Compared to a /24 subnet, it offers more scalability but requires greater management to avoid network congestion.

• Total IPs: 4,096
• Usable IPs: 4,094
• Subnet Mask: 255.255.240.0

c. /30 Subnet

A /30 subnet is much smaller than a /24, with only 2 usable IPs. It’s often used for direct links between two networking devices, where only two addresses are needed. It minimizes IP waste, making it ideal for specific, low-demand connections.

• Total IPs: 4
• Usable IPs: 2
• Subnet Mask: 255.255.255.252

d. /28 Subnet

A /28 subnet supports 14 usable IPs, suitable for small segments within a larger network or for networks with limited devices, like a set of servers. It’s smaller than a /24 but still provides enough IPs for minimal device setups.

• Total IPs: 16
• Usable IPs: 14
• Subnet Mask: 255.255.255.240

6. Final Thoughts

A /24 subnet is one of the most practical and commonly used subnet sizes in networking. Its balance between scalability and manageability makes it ideal for a wide range of networks—from home setups and small businesses.

The simplicity of the 255.255.255.0 subnet mask makes the /24 subnet both easy to understand and highly adaptable. Understanding the structure and limitations can help you optimize device allocation and network performance.

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