What is a Subnet Mask?

When you connect a computer to the Internet, you need to configure the TCP/IP protocol. The TCP/IP protocol requires you to enter the IP address, subnet mask as well as a default gateway in the configuration settings.

A TCP/IP protocol is divided into networks and subnetworks. This article will provide you with a general idea about what is a subnet mask.

Subnet Mask

The subnet mask helps a TCP/IP protocol determine is a host is on the local subnet or on a remote network. The parts of IP address that are used for the network and host addresses is not fixed. Thus, the network and host addresses cannot be determined until the required information is filled. Another 32-bit number then supplies this information.

The 32-bit number is called as the subnet mask. It helps differentiate the network component of an IP address by dividing it into a network address and host address. For example, is a subnet mask. The binary notation equals 11111111 for 255. Thus, the subnet mask is actually interpreted as 11111111.11111111.11111111.00000000.

The first 24 bits i.e. the ones in the subnet mask indicate the network address. The last remaining zeros or 8 bits indicates the host address.

You can visit http://www.internic.net to find the valid subnets and subnet masks that can be used on a TCP/IP network. This is all about what is a subnet mask. The above information will give you a fair idea about the use of a subnet mask when connecting to the Internet.