.\" 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
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    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
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY Bill Paul AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD: head/share/man/man5/ethers.5 140567 2005-01-21 10:46:36Z ru $
.\"
.Dd April 12, 1995
.Dt ETHERS 5
.Os
.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:
.Pp
.D1 Ar ethernet-address fully-qualified-host-name
.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
.Tn NIS
.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 8
.Sh HISTORY
The
.Nm
format is based on the format used in SunOS 4.1.x.