each computer is given a mac address by its computer maker. the way for giving mac addresses to computers, created by xerox, is used. mac addresses have 48-bits (how many 1s or 0s it has in it). as each of the twelve entries can have 16 possible values (0 through 9 and a through f), there are 1612 or 248 (or 281,474,976,710,656) possible mac addresses. mac addresses identify many things, such as the type of device being used.