Subnet Mask

Subnet Mask – What Is It?

Subnet mask is a concept that refers to the functioning of Internet Protocol addresses and is used as a separation tool for the components of an IP address. The purpose of the separation is to provide a way for your PC to identify what IP addresses are local and which IP addresses are remote.

Subnet Mask IP Address Anatomy

In order to understand how a subnet mask works you must first be familiar with the components of an Internet Protocol (IP) address. An IP address is comprised of two different components which include the network address which identifies the network portion of the IP address and the host address which tells you what portion of the IP address is available for host use.

An IP address is an address that uniquely identifies each device which is connected to the Internet. The address has four sets of numbers separated by a decimal and contains 32-bits. This means that the network address has a set of numbers and a host address has another set of numbers.

IP addresses are divided into what is referred to as a class which is a division of IP addresses which are subnet mask addresses. Class A IP addresses are occupied by larger networks, Class B by medium sized networks, and Class C by smaller networks such as a home network or small business that may use a subnet mask.

Subnet Mask Roles

The role of the subnet is to divide the host IP address into a subnet. The subnet mask is the 32-bit number we described above in the IP address section which masks the IP address and divides the IP into a network and host address.

A subnet mask is constructed by setting the network bits completely to the number “1” and then setting the entire host bits to the number “0.” The end result may look something like this, look how the subnet mask is displayed:

IP Address: 10011100.10011010.01010001.00111000
Subnet Mask: 11111111.11111111.11111111.11110000
Result: 0011100.10011010.01010001.00110000

In order to calculate the number of hosts which are available on the subnet you simply calculate the number of bits starting on the right hand side until you reach the first number “1.” Then you use an algorithm calculation to determine how many hosts are on the subnet.

This is a simplified version of a rather technical explanation. If you are a novice then the subnet mask is best understood by the process of using a telephone number with an area code. If you are making a call from a telephone number with a 415 area code to a telephone with a 914 area code then this tells the telephone exchange that the call must be routed to the appropriate technology that knows how to find the 914 number.

Subnet Masks And Why They Are Used

Subnet masks are a necessary part of Internet Protocol due to the fact that your router has to determine the best way to send the information across the Internet. The subnet provides the router with the information it needs to send information packets over the Internet in the most efficient manner by knowing which paths to use to get the information to its destination in the fastest way possible for a subnet mask.