.\" Copyright (c) 1995
.\"	Bill Paul <wpaul@ctr.columbia.edu>.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
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.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by Bill Paul.
.\" 4. Neither the name of the author nor the names of any co-contributors
.\"    may be used to endorse or promote products derived from this software
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.\" $FreeBSD$
.\"
.Dd April 12, 1995
.Dt ETHERS 5
.Os FreeBSD
.Sh NAME
.Nm ethers
.Nd ethernet address database
.Sh DESCRIPTION
The
.Nm
database contains information regarding known 48-bit ethernet addresses
of hosts on an Internetwork.
The data is stored in a file called
.Pa /etc/ethers
in the following format:
.Bd -unfilled -offset indent
.Pa ethernet-address fully-qualified-host-name
.Ed
.Pp
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.
A ``+'' at
the start of a line will cause the
.Xr ethers 3
library functions to use data stored in the
.Xr NIS 4
.Pa ethers.byname
and
.Pa ethers.byaddr
maps in addition to the data in the
.Pa /etc/ethers
file.
.Pp
An ethernet address is expressed in
.Tn ASCII
form as "x:x:x:x:x:x" where
.Ar x
is a hexadecimal value between 0x00 and 0xFF.
The address values
should be in network order.
Hostnames specified in the
.Pa /etc/ethers
database should correspond to entries in the
.Xr hosts 5
file.
.Pp
The
.Fn ether_line
function in the standard C library can be used to break individual
lines in the
.Pa /etc/ethers
database into their individual components: a binary Ethernet address
stored as an
.Pa ether_addr
structure, and a hostname stored as a character string.
.Sh FILES
.Bl -tag -width /etc/services -compact
.It Pa /etc/ethers
The
.Nm
file resides in
.Pa /etc .
.El
.Sh SEE ALSO
.Xr ethers 3 ,
.Xr yp 4
.Sh HISTORY
The
.Nm
format is based on the format used in SunOS 4.1.x.