The allocation of addresses to organizations was difficult. Introduction categories of networks greatly facilitated this task. But it became impractical when using multiple computers in the node. For rational use of organized subnet, which consists of the class A, B or C and contains a field called (subnet field). For this value requires more bits, which, in turn, belong to the host part. Thus, one network can be divided into two subnets (at least). To determine the address in this case becomes very difficult. Programming began to use a new term - the mask of the subnet. It implies the length of the addresses of each subnet. To determine the mask, you need to do the following: to begin to record the IP address in binary form. To make this procedure requires the discharges that belong to the network and subnet parts, to replace the units, all values that belong to the host portion, on the zeros. In the end, you will receive the mask of the subnet.
If you do not know your IP address, you can use the second method. In the network connections properties most often indicated mask subnet. To view it, follow these steps: open the start menu; then go to the "control Panel". In the opened window you will see a list of CPU tasks. Go to "Network connections". Visiteuses in the list find "Internet Protocol (TCP/IP)". Open the menu "Properties". In the settings select "Mask subnet".
Sometimes it happens that you configure all subnets computer automatically gets the properties of "Internet Protocol (TCP/IP)" does not display them. In this case, you can do so: open a Windows command prompt. To do this go to "start" then "All programs", Accessories, "Command prompt". Dialog box opens. Type the command ipconfig, then you will see a list of all addresses of networks and subnets available. Find the desired mask.