The eui64 database contains information regarding known IEEE EUI-64s of hosts. The data is stored in a file called /etc/eui64 in the following format:
Items are separated by any number of blanks and/or tab characters. A # at the start of a line indicates the beginning of a comment that extends to the end of the line. Valid lines may also contain comments. A + at the start of a line will cause the eui64(3) library functions to use data stored in the NIS eui64.byname and eui64.byid maps in addition to the data in the /etc/eui64 file.
An EUI-64 is expressed in ASCII form as "x-x-x-x-x-x-x-x" where x is a hexadecimal value between 0x00 and 0xFF. The address values should be in network order. Hostnames specified in the /etc/eui64 database should correspond to entries in the hosts(5) file.