ARPD(8)                     System Manager's Manual                    ARPD(8)

     farpd — ARP reply daemon

     farpd [-d] [-i interface] [net ...]

     farpd replies to any ARP request for an IP address matching the specified
     destination net with the hardware MAC address of the specified interface,
     but only after determining if another host already claims it.

     Any IP address claimed by farpd is eventually forgotten after a period of
     inactivity or after a hard timeout, and is relinquished if the real owner
     shows up.

     This enables a single host to claim all unassigned addresses on a LAN for
     network monitoring or simulation.

     farpd exits on an interrupt or termination signal.

     Note: The program name farpd has been changed in Debian GNU/Linux from
     the original name (arpd) to avoid name clash with other ARP daemons.

     The options are as follows:

     -d      Do not daemonize, and enable verbose debugging messages.

     -i interface
             Listen on interface.  If unspecified, farpd searches the system
             interface list for the lowest numbered, configured ``up''
             interface (excluding loopback).

     net     The IP address or network (specified in CIDR notation) or IP
             address ranges to claim (e.g. ``'', ``'' or
             ``''). If unspecified, farpd will attempt to
             claim any IP address it sees an ARP request for.  Mutiple
             addresses may be specified.


     pcapd(8), synackd(8)

     farpd will respond too slowly to ARP requests for some applications. In
     order to ensure that it does not claim existing IP addresses it will send
     two ARP request and wait for a reply. This slowness affects the nmap
     network scanning tool, and possibly others, which uses by default ARP
     when scanning local networks. The answers from farpd will come after the
     tool has timeout waiting for the ARP replies and, consequently, IP
     addresses claimed by farpd will not be discovered.

     Additionally, farpd sends the ARP replies to the broadcast address of the
     network and not to the host that send the ARP request. Some systems and
     applications (notably nmap) will not handled these requests and expect
     directed ARP replies (i.e. targeted specifically to the host that sent
     the request and not to the network)

     Dug Song ⟨dugsong@monkey.org⟩, Niels Provos ⟨provos@citi.umich.edu⟩

                                August 4, 2001