NetBSD/usr.sbin/dhcp/relay/dhcrelay.8

.\"	dhcrelay.8
.\"
.\" 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
.\" Enterprises, see ``http://www.vix.com''.
.TH dhcrelay 8
.SH NAME
dhcrelay - Dynamic Host Configuration Protocol Relay Agent
.SH SYNOPSIS
.B dhcrelay
[
.B -p
.I port
]
[
.B -d
]
[
.B -q
]
[
.B -i
.I if0
[
.B ...
.B -i
.I ifN
]
]
.I server0
[
.I ...serverN
]
.SH DESCRIPTION
The Internet Software Consortium DHCP Relay Agent, dhcrelay, 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.
.SH SYSTEM REQUIREMENTS
You must have the Berkeley                         
Packet Filter (bpf) configured in your NetBSD kernel.   You must have  
at least one /dev/bpf* file for each broadcast network interface that
is attached to your system. 
.SH OPERATION
.PP
The DHCP Relay Agent listens for DHCP requests on all interfaces
attached to a host, unless one or more interfaces are specified on the
command line with the
.I -i
flag.
.PP
When a query is received, dhcrelay 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
It is possible to specify a set of interfaces on which dhcrelay will
listen, so that if dhcrelay is connected through one interface to a
network on which there is no DHCP server, but is connected on another
interface to a network on which there is a DHCP server, it will not
relay DHCP and BOOTP requests from the network on which the server
exists to that server.   This is an imperfect solution.
.SH COMMAND LINE
.PP
The names of the network interfaces that dhcrelay should attempt to
configure may be specified on the command line using the
.I -i
option.  If no interface names
are specified on the command line dhcrelay will identify all network
interfaces, elimininating non-broadcast interfaces if possible, and
attempt to configure each interface.
.PP
If dhcrelay should listen and transmit on a port other than the
standard (port 67), the
.B -p
flag may used.  It should be followed by the udp port number that
dhcrelay should use.  This is mostly useful for debugging purposes.
If the
.B -p
flag is specified, the relay agent will transmit responses to clients
at a port number that is one greater than the one specified - i.e., if
you specify
.B -p
67, then the relay agent will listen on port 67 and transmit to port
68.   Transmissions to servers will be sent to the same port number
that it specified in the
.B -p
flag.
.PP
Dhcrelay will normally run in the foreground until it has configured
an interface, and then will revert to running in the background.
To run force dhcrelay to always run as a foreground process, the
.B -d
flag should be specified.  This is useful when running dhcrelay under
a debugger, or when running it out of inittab on System V systems.
.PP
Dhcrelay will normally print its network configuration on startup.
This can be annoying in a system startup script - to disable this
behaviour, specify the
.I -q
flag.
.PP
The name of at least one DHCP server to which DHCP and BOOTP requests
should be relayed must be specified on the command line.
.PP
.SH SEE ALSO
dhclient(8), dhcpd(8), RFC2132, RFC2131.
.SH AUTHOR
.B dhcrelay(8)
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
.B http://www.vix.com/isc.
To learn more about Vixie
Enterprises, see
.B http://www.vix.com.
.PP