Items are separated by any number of SPACE and/or TAB characters. A ``#'' indicates the beginning of a comment extending to the end of line.
The standard form for Ethernet addresses is x:x:x:x:x:x, where x is a hexadecimal number between 0 and FF, representing one byte. The address bytes are always in network order. Host names may contain any printable character other than a SPACE, TAB, NEWLINE, or comment character. It is intended that host names in the ethers file correspond to the host names in the hosts(4tcp) file.
RFC 903