Subnet masking explained

In a local area network, network devices are connected in close proximity with each other and require logical grouping to work efficiently. This logical grouping can be referred to as a subnet. Subnetting is used in various organizations around the world to increase the efficiency of their networks while also providing sound security measures.

The Importance of Subnetting

The main purpose of subnet application is to divide the network into two or more subnets. It increases network security while decreasing congestion at the same time. It provides multiple advantages to various administrative departments of companies by separating the network between different departments. Additionally, the importance of subnetting can be summed up into three points below.

Management of IP addresses:
In a vast network with multiple hosts (typically thirty), it can be a complex affair to organize them in an efficient manner. Subnetting allows us to break larger networks into smaller ones.

Network traffic is reduced:
The broadcast traffic on network boundaries is reduced because of the creation of smaller networks, resulting in smaller broadcast domains.

Simplifying the process:
Subneting networks can break up large networks into smaller networks which results in a simpler and narrower troubleshooting process.

What is a Subnet Mask?

A subnet mask refers to a range of IP addresses in use in a network, used to designate and segregate smaller networks called sub-networks under them. This system can also include local area networks. Typically, systems falling within the same sub-network can communicate directly with each other while systems belonging to different networks can use a router for communication. A subnet mask is written using the “dotted-decimal” notation system and consists of 4 bytes or 32 bits.

Binary Representation example:
10101000 11000000 00010010 0011011

Dotted Decimal Notation example:

The Use of Subnet Masking

A subnet mask is typically used to hide or “mask” a part of the system’s IP address. This leaves only the host part as the sole machine identifier. A standard network address contains both the network address as well as the subnet number, which together support a two-level addressing scheme. This allows the flow of network traffic between hosts to be differentiated based on a prior network configuration.

Subnet masking is typically used in large organizations that have different departments for each operation. For example, an organization can use the network for its internal or intranet hosts. Certain administrative departments like Human Resources or Accounts, may want to be in a restricted part of the network as they deal with sensitive personal information like employee data or payroll information. As the default subnet mask of any Class C network is, every computer in the network can communicate directly, store information, and send messages amongst themselves. Subnet masking can be used to isolate the networks of various departments that require a level of secrecy and isolation.

The Different Types of Networks

Generally, networks can be classified into three broad types or “classes” depending on their size.

  • Class A: The biggest and broadest class of networks falls under the Class A type. They can consist of up to 224 nodes and have an address ranging from 1.0000 to The zeros get replaced by the respective node addresses.
  • Class B: They are smaller in comparison as compared to the Class A type of networks. Network addresses range from to The last two zeros are replaced by the respective node addresses.
  • Class C: These are the smallest of networks that have a capacity of 254 nodes at the most. The address range is from to

The Advantages of Using Subnet Masks

Proper implementation of subnet masking can result in an increase in router efficiency, simplifies network management, and can also be arranged in a hierarchical architecture. The advantages are listed below:

  1. Unnecessary Broadcasts are Prevented:
    Broadcasts refer to small bits of information that a computer can send to other devices on a common network. Broadcasts can also be caused when a computer gets infected by malware or virus which can spread to the other devices present on the network. Even though it may not be a problem for smaller networks, large organizations with large networks may face severe hazards. Subnet masking allows the IP address to be divided among smaller subnets, thus stopping the broadcast from spreading across the entire network.
  2. Security is Increased:
    Subnet masking can divide the vital functions of one network into different sub-networks. This makes it possible to deploy separate security measures like firewalls or anti-virus software into separate sub-networks. Each process is completed faster by efficiently allowing system administrators to address issues individually.
  3. Helps in Administration and Organization:
    Subnet masking is the best when it comes to separating networks based on departments. Normally, when different departments co-exist on a single, large network, access restrictions for different departments have to be entered manually. Subnet masking simplifies this by placing departments on separate subnets for better security deployment.
  4. Increases Overall Efficiency of the Network:
    In large networks, especially those belonging to large corporations or multinational companies, the broadcasting domain is large and the process takes more time to complete. This is because the signal must reach every possible recipient before it reaches the designated one. By using subnet masking, network administrators can decrease the size of the broadcast domain by segregating networks. This results in a quicker process, where the data reaches its destination faster.

Subnet masking provides network administrators with increased flexibility while defining the relationships among network hosts. In other words, subnet masking has the ability to filter traffic between subnets by limiting access in an organized way. It also increases the bandwidth available, making the network efficient and reliable.