The EUI-64 format interface ID is derived from the 48-bit MAC address by inserting the hexadecimal number fffe between the upper 3 bytes (OUI field) and the lower 3 vendor assigned bytes of the MAC address. Then, the seventh bit of the first octet is inverted. (In a MAC address, this bit indicates the scope and has a value of 1 for global scope and 0 for local scope; it will be 1 for globally unique MAC addresses. In the EUI-64 format, the meaning of this bit is opposite, so the bit is inverted.)