People use a subnet mask to identify what specific part of an Internet Protocol address is allotted for the host as well as the particular area reserved for the network. Also referred to as the netmask, this information is vital, as it is necessary to measure easily the specific parts for the host and the network. Generally, this information is very important because it is used to indicate whether different IP addresses belong to the same subnet. Learning all these things are really important as they can spell the successful flow or even the failure of a system to work smoothly and properly.

All in all, there are 32 bits constituting subnet masks, which are clearly represented by a block of zeroes and a block of ones. In this sequence, the zeroes are basically used to identify the part of the host. Meanwhile, the subnet mask of the so-called classful networks is set at 255.255.255.0, 225.225.0.0, or 255.0.0.0. Furthermore, the Classless Inter-Domain Routing (CIDR) notation is primarily a shorter form of what is used to express these subnet masks. This particular notation basically indicates the number of the network, as well as the netmask’s binary notation separated in between by a slash. An example of this CIDR notation would be 192.0.2.96/24.

How to Use a Subnet Mask to Determine the Portions of the Host and the Network in a Specific IP Address

With the use of a subnet mask, people can easily identify the specific network address for a particular IP address. The first thing they need to do is transpose the octal addresses into a binary form. After doing so, they must perform a simple bitwise AND action. For instance, the octal address for the IP address 156.154.81.56 is transposed as 10011100.10011010.01010001.00111000, while the subnet mask 255.255.255.240 can be converted into its binary form 11111111.11111111.11111111.11110000. After performing a bitwise AND action on these data, the exact result will be 10011100.10011010.01010001.00110000.

The Importance of Subnet Masks to Internet Protocol Networks

When managing an IP network, subnet masks are of great importance because they serve as a reliable means of communication. The defined subnet mask and the targeted IP address are used by network devices to identify whether the host is using a remote network or a local subnet. Usually, a network device sends an Address Resolution Protocol request when using a local subnet. The purpose of this operation is basically to recover the questioned system’s MAC address in order to relay communications to the Data Link Layer of the OSI Model.

Meanwhile, a different action usually happens when a remote network is used. In this case, packets are then routed by network devices toward the gateway in the routing table, which is an e-document storing the routes to the computer network’s different nodes. If there is no entry in the routing table that specifically matches network, a default route is necessary to send the packets. When there is no identifiable default route, the packets cannot go anywhere and are simply dropped in the process.

Will Spencer is a computer network and Internet security expert and has written several articles on subnets such as Understanding the Subnet Mask and Subnet: What You Need to Know Info. Visit A Concise Look at the Different Important Aspects Pertaining to Subnet Masks.