What is Subnet Mask?

Every device has an IP address with two pieces: the client or host address and the server or network address. IP addresses are either configured by a DHCP server or manually configured (static IP addresses). The subnet mask splits the IP address into the host and network addresses, thereby defining which part of the IP address belongs to the device and which part belongs to the network.

What is Subnet Mask?

A subnet mask is a 32-bit number created by setting host bits to all 0s and setting network bits to all 1s. In this way, it separates the IP address into the network and host addresses.

The “255” address is always assigned to a broadcast address, and the “0” address is always assigned to a network address. Neither can be assigned to hosts, as they are reserved for these special purposes.

The IP address, subnet mask, and gateway or router comprise an underlying structure – the Internet Protocol – that most networks use to facilitate inter-device communication.

When organizations need additional sub-networking, subnetting divides the host element of the IP address further into a subnet. The goal of subnet masks is simply to enable the subnetting process. The phrase “mask” is applied because the subnet mask essentially uses its 32-bit number to mask the IP address.

subnet mask

Structure of Subnet Mask

A subnet mask distinguishes the network identifier from the host identifier in an IP address but is not restricted by the same rules as the class-based method. Like an IP address, it is made up of four numbers. These numbers can range from 0 to 255.

In the class-based method, each of these four numbers can only have a maximum value of 255 or a minimum value of 0. The four numbers are then arranged as contiguous maximum values followed by contiguous minimum values. The maximum values represent the network identifier and the minimum values represent the host identifier. For example, is a valid subnet mask as opposed to The subnet mask identifies the network identifier as the first two digits of the IP address.

How to use it?

It is used by the router to cover up the network address. It shows which bits are used to identify the subnet.

Every network has its unique address, Like here, the class B network has network address, which has all zeroes in the host portion of the address.

Example IP address: 11000001. Here 1st and 2nd bits are 1, and the 3rd bit is 0; hence, it is class C.

subnet mask

The above example shows how IP addresses should be deconstructed, which makes it simple for Internet routers to find the right Network to route data into. However, in a Class A network, there could be millions of connected devices, and it could take some time for the router to find the right device.

What is a Subnet Mask Calculator?

Some know how to calculate subnet masks by hand, but most use subnet mask calculators. There are several types of network subnet calculators. Some cover a wider range of functions and have greater scope, while others have specific utilities. These tools may provide information such as IP range, IP address, subnet mask, and network address.

Here are some of the most common varieties of IP subnet mask calculators:

  • An IPv6 IP Subnet Calculator maps hierarchical subnets.
  • An IPv4/IPv6 Calculator/Converter is an IP mask calculator that supports IPv6 alternative and condensed formats. This network subnet calculator may also allow you to convert IP numbers from IPv4 to IPv6.
  • An IPv4 CIDR Calculator is a subnet mask adjustment and Hex conversion tool.
  • An IPv4 Wildcard Calculator reveals which portions of an IP address are available for examination by calculating the IP address wildcard mask.
  • Use a HEX Subnet Calculator to calculate the first and last subnet addresses, including the hexadecimal notations of multicast addresses.
  • A simple IP Subnet Mask Calculator determines the smallest available corresponding subnet and subnet mask.
  • A Subnet Range/Address Range Calculator provides start and end addresses.

subnet mask


Understanding what a subnet mask is may be impossible until you begin to understand how IP addresses work and why networks use subnetting. That’s why the answer to “What it is?” isn’t completely straightforward.

With this said, you should now have basic knowledge of how IPv4 addresses communicate data between and within networks. The administrators of those networks may choose to use subnetting out of concern for security, routing efficiency, and network speed or to preserve more public IPv4 addresses. Usually, it’s a combination of multiple reasons.

If you choose to utilize subnetting in your network, you’ll need to use subnet masks to ensure that inbound traffic is routed to and from the correct host devices. Even if you run a relatively small system, it can play an integral part in its reliable and smooth operation.


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