What Is a Subnet Mask? Definition, Working, and Benefits

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Written By Nidhi Sharma

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Subnet masks are used to determine the network ID or host ID of an IP network during subnetting.

A subnet mask can be defined as a 32-bit address that segregates an IP address into network bits that identify the network, and host bits that are used to identify the host device on that network. This article will explain what a subnet mask is and how it can be beneficial to network infrastructure.

What is a Subnet Mask?

A subnet mask, a 32-bit address, segregates an IP address into host bits and network bits. It contains several IP addresses that subnets can use. The subnet is a smaller network within an extensive network.

Subnet masks are technical terms that are used within a network. Routing devices, or switches, rely on subnet masks to route data packets to the appropriate destinations.

The subnet mask is not used to identify data packets as they travel over the internet. Instead, the destination IP address is revealed. To deliver the data packet to the correct place, routers match the destination IP address with the subnet mask.

Let's look at an analogy to better understand the subnet mask concept. Let's say that a user named Davis writes a letter to Tom. Davis writes this letter to Tom's workplace, rather than his home. Tom's workplace is large and has many co-located departments. To ensure that no correspondence is lost or misplaced, Tom's administrative team sorts mail by the department and not by employee names.

The team receives Davis's letter and identifies Tom as a member of the HR department. The letter is therefore sent to the HR department and not Tom. The HR department then gives the letter to Tom.

The above example shows Tom representing an IP address and the HR department as a subnet mask. Because the letter was already matched to Tom's department, Davis quickly organized Davis's mail into a list of possible recipients.

The administrative team would not have spent the time to locate Tom's desk if they didn't do this initial sorting.
Let's now look at a real-world example. A data packet addresses the IP number This is a class-C network. The IP address can be split into a network address and a host address. Here, the class C network is represented by the network portion, which is '192.0.4. The network routers then deliver the data packet to the network identified as 192.0.4.

Once the packet arrives at the correct network, the router consults the routing table to forward the packet further. The router uses the data packet's subnet address of for binary math, to observe the device address "16", and calculate the subnet to which it should forward the packet.

After determining the target subnet it sends the packet to the router responsible for delivering data packets within the subnet. The data packet is then delivered to the destination IP address at

Representation For Subnet Masks

Subnetting is the process of logically splitting an IP network into multiple networks. This network subdivision allows for better use of IPv4 addresses and makes data routing in the network more secure and efficient.

An IP address is assigned to new devices that connect to networks. The IP address (IPv4) is a 32-bit numeric address. It has four numbers separated by periods.

Each octet represents the group of numbers in a block. Each octet has a number that ranges from 0 to 255. Without the subnet mask, it is impossible to distinguish between the network and the host portions of such IP addresses.

Let's take an example:

An IP address may be used to identify a device.

The subnet mask above for the IP network:

One can represent the subnet mask and IP address as:

Subnet masks are essential for subnetting. You can assign IP addresses to a network by making minor adjustments to the subnet mask. A household home network, for example, has a subnet mask standard of

This means that 254 IP addresses can be used within the defined network. This means that you can connect up to 254 internet-enabled devices, such as phones, computers, and IoT gadgets to your home network to access the internet.

A device can also observe the network and host bits of another device's IP address to determine if they are on the same network. Subnet masks are used by devices to exchange information with devices in the same or other networks.

How Does Subnetting Work?

Subnetting is essential for creating efficient and fast computer networks. Large companies that plan to expand their technological capabilities will need to be able to manage and organize their networks effectively as they grow.

When traffic has reliable routes across the network, complex networks can become resilient. Traffic would be unable to travel efficiently overall routes without adequate data paths. This would lead to congestion and bottlenecks, which would affect the network's performance.

Subnets enable network traffic to be passed through a minimal number of routers. Data packets need to travel a shorter distance to reach their destination by following mini-routes within a larger network.

An IP address acts as an identity for hardware devices in a network. If the IP addresses are logically organized and understood, it is possible to locate a specific device. Subnetting is where you come in. Subnetting not only allows you to locate network equipment but also helps maintain order and efficiency across the network.

Computer networks can have thousands of interconnected devices. The IP addresses of these devices can create complicated routes for network traffic. Subnetting limits the use of IP addresses to a small number of devices.

Network engineers can use sub-networks to sort data. This ensures that traffic does not touch every router in the network. Engineers are responsible for matching each IP address with the subnet mask.

A subnet mask acts like an IP address and identifies the network as well as the host parts within the original address. This helps to identify the routes that data should be sent to a specific destination. The network routers can use the subnet mask to match the destination's IP address to the data packet.

Subnetting Has Many Benefits

Network administrators have better control over their networks via subnetting. This includes traffic, data packets, and subnets. It improves network performance and security. Subnetting also ensures efficient use of IP addresses.

Let's explore some of the key benefits of subnetting.

1. Efficient Data Routing

Broadcast traffic can cause severe bottlenecks on larger networks. Broadcasting means that data packets travel to all nodes on the network. You can segregate broadcast domains into smaller sections with subnetting.

Subnetting allows for fewer broadcast traffic to interact with each other, which makes data routing more efficient and direct.

Subnets allow communication and interaction between multiple devices on smaller networks, which reduces the amount of communication traffic across larger networks where different instruments are interconnected simultaneously.

Let's look at an analogy. Let's say 60 people connect via Skype conference calls. All 60 people could talk simultaneously on Skype, which would lead to chaos and noise, making communication difficult. It's possible to make the session more productive and peaceful if you break down these 60 people into 12 breakout areas.

Subnet masks are crucial in this regard as they make sure that traffic stays within the subnet. Network congestion can be avoided and the network load is significantly reduced. Subnetting reduces the distance that data packets must travel to reach a network. This makes data routing more efficient. This improves network performance and speeds.

2. Network Security Enhanced

Many connected devices are necessary for enterprises with extensive local networks. This is because they can handle a significant amount of data traffic. Subnets are a better option than one large network to protect in such cases.

Let's suppose hackers attack a smaller network segment. Only the affected network segment is affected and compromised in such an attack.

The attackers can only access the devices in the subnet they are targeting, but other devices in the larger network are invisible to them. This decreases the attack surface since intruders cannot gain access to all devices.

Network managers can use small subnets for identifying and addressing external threats. They control network traffic using route maps, quality-of-service mechanisms, and network access control lists (ACLs).

Route map configurations are used to route data packets, without the use of routing tables. QoS services prioritize high-performance applications and adjust network traffic. ACLs control traffic to subnets. These network applications require subnets to enhance network security.

They also aid in the isolation of legitimate local networks. They also control access to all devices on the network. This allows you to protect specific files and processes from unauthorized access. Remote network access can also be restricted.

3. Long-Term Use of IPv4 Addresses

It was easy to capture IP addresses with the advent of the internet. IPv4, the first version of the Internet Protocol, was released in 1980. It became the standard communication protocol for internet users.

History Computer (Nov. 20,21) reported that IPv4 was responsible for approximately 94% of all internet traffic. As IPv4 addresses became scarce, the IP address stock started to shrink over time, as intelligent devices like personal computers, televisions, and speakers grew in number. Subnetting was developed to increase the use of a single public IP address.

Instead of each device having a unique IP address (which is what it used to be), a network can have multiple IP addresses within the same IP network. Each device on the network will have a section that defines the network's IP address and another part that specifies its subnet. Subnetting allowed IPv4 to be used as an internet standard over a longer period.


Large corporations employ network engineers and network administrators to subnet their computer networks. This helps to protect their networks from external threats, improve routing efficiency, preserve public IPv4 addresses, as well as increase network speed and performance. Subnet masks are used to route inbound traffic to the intended hosts in subnetting. Subnet masks are reliable and smooth regardless of the size of the subnets.

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