The original IEEE 802 MAC address comes from the original Xerox Ethernet addressing scheme.[1] This 48-bit address space contains potentially 2^48 or 281,474,976,710,656 possible MAC addresses.
Addresses can either be universally administered addresses or locally administered addresses.
Universally administered and locally administered addresses are distinguished by setting the second least significant bit of the most significant byte of the address. If the bit is 0, the address is universally administered. If it is 1, the address is locally administered. In the example address 06-00-00-00-00-01 the most significant byte is 06 (hex), the binary form of which is 00000110, where the second least significant bit is 1. Therefore, it is a locally administered address
因為有一個全球統一分配的和一個是本地分配的 標誌位。所以是2^47次方
這是國外教材上的：
The original IEEE 802 MAC address comes from the original Xerox Ethernet addressing scheme.[1] This 48-bit address space contains potentially 2^48 or 281,474,976,710,656 possible MAC addresses.
Addresses can either be universally administered addresses or locally administered addresses.
Universally administered and locally administered addresses are distinguished by setting the second least significant bit of the most significant byte of the address. If the bit is 0, the address is universally administered. If it is 1, the address is locally administered. In the example address 06-00-00-00-00-01 the most significant byte is 06 (hex), the binary form of which is 00000110, where the second least significant bit is 1. Therefore, it is a locally administered address