


dhcrelay(8)                                           dhcrelay(8)


NAME
       dhcrelay  -  Dynamic  Host  Configuration  Protocol (DHCP)
       Relay Agent

SYNOPSIS
       dhcrelay [ -p port ] [ -d ] [ -q ] [ -i if0 [ ...  -i  ifN
       ] ] server0 [ ...serverN ]

DESCRIPTION
       The  Internet Software Consortium DHCP Relay Agent, dhcre-
       lay, provides a means for relaying DHCP and BOOTP requests
       from  a  subnet to which no DHCP server is directly to one
       or more DHCP servers on other subnets.

SYSTEM REQUIREMENTS
       You must have the Berkeley Packet Filter (bpf)  configured
       in  your  kernel.    You  must have at least one /dev/bpf*
       file for each broadcast network interface that is attached
       to your system.

OPERATION
       The  DHCP  Relay  Agent  listens  for DHCP requests on all
       interfaces attached to a host, unless one or  more  inter-
       faces  are specified on the command line with the -i flag.

       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  net-
       work from whence the original request came.

       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 solu-
       tion.

COMMAND LINE
       The names of the network interfaces that  dhcrelay  should
       attempt  to configure may be specified on the command line
       using the -i option.  If no interface names are  specified
       on  the  command  line  dhcrelay will identify all network
       interfaces, eliminating non-broadcast interfaces if possi-
       ble, and attempt to configure each interface.

       If  dhcrelay  should  listen  and transmit on a port other
       than the standard (port 67), the -p  flag  may  used.   It
       should  be  followed  by the udp port number that dhcrelay
       should use.  This is mostly useful for debugging purposes.

       Dhcrelay  will normally run in the foreground until it has
       configured an interface, and then will revert  to  running



                                                                1





dhcrelay(8)                                           dhcrelay(8)


       in the background.  To run force dhcrelay to always run as
       a foreground process, the -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.

       Dhcrelay will normally print its network configuration  on
       startup.   This can be annoying in a system startup script
       - to disable this behaviour, specify the -q flag.

       The name of at least one DHCP server  to  which  DHCP  and
       BOOTP  requests should be relayed must be specified on the
       command line.


SEE ALSO
       dhclient(8), dhcpd(8), RFC2132, RFC2131.

AUTHOR
       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 http://www.vix.com/isc.  To learn
       more about Vixie Enterprises, see http://www.vix.com.


































                                                                2


