farpd (8)
replies to any ARP request for an IP
address matching the specified destination with the hardware MAC address
of the specified but only after determining if another host already claims
it. Any IP address claimed by 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. exits on an interrupt or
termination signal. Note: The program name 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: Do not daemonize, and enable
verbose debugging messages. Listen on If unspecified, searches the system
interface list for the lowest numbered, configured ‘‘up’’ interface (excluding
loopback). 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,
will attempt to claim any IP address it sees an ARP request for. Mutiple
addresses may be specified.
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 will come after the tool has timeout waiting for the ARP replies
and, consequently, IP addresses claimed by will not be discovered. Additionally,
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 Niels Provos
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