>>Well... If you are running a class C network with a netmask of 255.255.255.0, then the first 3 octals have to be the same for the person to be on the same subnet. For instance, 192.168.0.x, where 'x' is any unique number between 1 and 254.
>
>"octals"?

An IPv4 address has 4 octals. For instance: 192.168.0.1. The 192 is an octal, the 168, 0, and 1. Each section is limited to the numbers 0 thru 255, or 2^8. This is because IPv4 is 32-bit addressing.

Make sense?

j