.\"	$OpenBSD: dhcrelay.8,v 1.12 2013/07/16 11:13:33 schwarze Exp $
.\"
.\" Copyright (c) 1997 The Internet Software Consortium.
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.\" THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
.\" CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
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.\" This software has been written for the Internet Software Consortium
.\" by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
.\" Enterprises.  To learn more about the Internet Software Consortium,
.\" see ``http://www.isc.org/isc''.  To learn more about Vixie
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.\"
.Dd $Mdocdate: July 16 2013 $
.Dt DHCRELAY 8
.Os
.Sh NAME
.Nm dhcrelay
.Nd Dynamic Host Configuration Protocol relay agent
.Sh SYNOPSIS
.Nm
.Op Fl do
.Fl i Ar interface
.Ar server1 Op Ar ... serverN
.Sh DESCRIPTION
The
.Nm
utility provides a means for relaying DHCP and BOOTP requests from a subnet
to which no DHCP server is directly connected to one or more DHCP servers on
other subnets.
.Pp
.Nm
listens for DHCP requests on a given interface.
When a query is received,
.Nm
forwards it to the list of DHCP servers specified on the command line.
When a reply is received, it is broadcast or unicast on the network from
whence the original request came.
.Pp
The name of at least one DHCP server to which DHCP and BOOTP requests
should be relayed,
as well as the name of the network interface that
.Nm
should attempt to configure,
must be specified on the command line.
.Pp
.Nm
supports relaying of DHCP traffic to configure IPsec tunnel mode
clients when listening on the
.Xr enc 4
interface.
The DHCP server has to support RFC 3046 to echo back the relay agent
information to allow stateless DHCP reply to IPsec tunnel mapping.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl d
.Nm
normally runs in the foreground until it has configured
an interface, and then reverts to running in the background.
This option forces
.Nm
to always run as a foreground process.
.It Fl i Ar interface
The name of the network interface that
.Nm
should attempt to configure.
At least one IPv4 address has to be configured on this interface.
.It Fl o
Add the relay agent information option.
By default, this is only enabled for the
.Xr enc 4
interface.
.El
.Sh SEE ALSO
.Xr dhclient 8 ,
.Xr dhcpd 8
.Sh STANDARDS
.Rs
.%A R. Droms
.%D March 1997
.%R RFC 2131
.%T Dynamic Host Configuration Protocol
.Re
.Pp
.Rs
.%A S. Alexander
.%A R. Droms
.%D March 1997
.%R RFC 2132
.%T DHCP Options and BOOTP Vendor Extensions
.Re
.Pp
.Rs
.%A M. Patrick
.%D January 2001
.%R RFC 3046
.%T DHCP Relay Agent Information Option
.Re
.Pp
.Rs
.%A B. Patel
.%A B. Aboba
.%A S. Kelly
.%A V. Gupta
.%D January 2003
.%R RFC 3456
.%T Dynamic Host Configuration Protocol (DHCPv4) Configuration of IPsec Tunnel Mode
.Re
.Sh AUTHORS
.An -nosplit
.Nm
was written by
.An Ted Lemon Aq Mt mellon@fugue.com .
.Pp
The current implementation was reworked by
.An Henning Brauer Aq Mt henning@openbsd.org .
.Sh BUGS
Relayed DHCP traffic could actually safely be protected by IPsec but,
like
.Xr dhcpd 8
and
.Xr dhclient 8 ,
.Nm
will bypass IPsec for all its traffic.