How to Determine IP Ranges From Subnet Mask

The logical or IP address of a computer is a combination of the address of the network and the address of the computer on that network. The subnet mask determines what part of the address is for the network and what part applies to the individual computer. To determine the ranges of an IP address from the subnet mask, you will need an understanding of the binary number system and how to convert decimal numbers to binary.

Instructions

1. Convert each part of the IP address to binary.

2. Convert each part of the subnet mask to binary.

3. Write the binary IP address above the binary subnet mask, matching each number position in the IP address with the same number position in the subnet mask.

4. Look at the subnet mask. Every position where there is a 1 is part of the network address. Everywhere there is a 0 is part of the available range of computer addresses. For example, a subnet mask of 11111111.11111111.11111111.00000000 (255.255.255.0) would indicate the first 24 numbers of the IP are used for the network address and the remaining eight are the available range of computer addresses.

Tips & Warnings

• The subnet mask must be all 1s and then all 0s. If you have a 1 after a 0, you have converted incorrectly.