| ETHERS(5) | File Formats Manual | ETHERS(5) | 
ethers —
ethers file maps Ethernet MAC addresses to host
  names. Lines consist of an address and a host name, separated by any number of
  blanks and/or tab characters. A ‘#’ character indicates the
  beginning of a comment; characters up to the end of the line are not
  interpreted by routines which search the file.
Each line in ethers has the format:
ethernet-MAC-address
  hostname-or-IPEthernet MAC addresses are expressed as six hexadecimal numbers separated by colons, e.g. "08:00:20:00:5a:bc". The functions described in ethers(3) and ether_aton(3) can read and produce this format.
The traditional use of ethers involved
    using hostnames for the second argument. This may not be suitable for
    machines that don't have a common MAC address for all interfaces (i.e., just
    about every non Sun machine). There should be no problem in using an IP
    address as the second field if you wish to differentiate between different
    interfaces on a system.
ethers file resides in
      /etc.ethers file format was adopted from SunOS and
  appeared in NetBSD 1.0.
| November 7, 2000 | NetBSD 10.0 |