farpd — ARP reply daemon

Authors

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

                                                 August 4, 2001                                          ARPD(8)

Bugs

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.

Description

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.

       -iinterface
               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.
               ``10.0.0.3'', ``10.0.0.0/16'' or ``10.0.0.5-10.0.0.15''). If unspecified, farpd will  attempt  to
               claim any IP address it sees an ARP request for.  Mutiple addresses may be specified.