dhcrelay - Dynamic Host Configuration Protocol Relay Agent
dhcrelay [ -p port ] [ -d ] [ -q ] [ -i if0 [ ... -i ifN
] ] server0 [ ...serverN ]
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 con
nected to one or more DHCP servers on other subnets.
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
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, elimininating non-broadcast interfaces if pos
sible, 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.
If the -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 -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 -p flag.
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 -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
dhclient(8), dhcpd(8), RFC2132, RFC2131.
dhcrelay(8) has been written for the Internet Software
Consortium by Ted Lemon <email@example.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.
Man(1) output converted with