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.\" $OpenBSD: dhcrelay.8,v 1.9 2009/09/03 11:56:49 reyk Exp $
.\"
.\" Copyright (c) 1997 The Internet Software Consortium.
.\" 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. Neither the name of The Internet Software Consortium nor the names
.\" of its contributors may be used to endorse or promote products derived
.\" from this software without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM 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 INTERNET SOFTWARE CONSORTIUM 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.
.\"
.\" 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
.\" Enterprises, see ``http://www.vix.com''.
.\"
.Dd $Mdocdate: September 3 2009 $
.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
.Pp
RFC 2132, RFC 2131, RFC 3046, RFC 3456
.Sh AUTHORS
.An -nosplit
.Nm
was written by
.An Ted Lemon Aq mellon@fugue.com .
.Pp
The current implementation was reworked by
.An Henning Brauer Aq 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.
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