arp(7P) 																   arp(7P)

NAME

       arp - Address Resolution Protocol

DESCRIPTION

       ARP is a protocol used to dynamically map between DARPA Internet and hardware station addresses.  It is used by all LAN drivers.

       ARP caches Internet-to-hardware station address mappings.  When an interface requests a mapping for an address not in the cache, ARP queues
       the message that requires the mapping, and broadcasts a message on the associated network requesting the address mapping if the	encapsula-
       tion  method has been enabled for the interface.  If a response is provided, the new mapping is cached and any pending message is transmit-
       ted.  ARP queues at most one packet while waiting for a mapping request to be responded to; only the most recently  ``transmitted''  packet
       is kept.

       To  facilitate  communications with systems that do not use ARP, calls are provided to enter and delete entries in the Internet-to-hardware
       station address tables.

   Application Usage:
       Each call takes the same structure as an argument.  sets an ARP entry, gets an ARP entry, and deletes an ARP entry.   These  calls  can	be
       applied to any socket descriptor s, but only by the super-user.	The structure contains:

       The  address  family for the must be for the it must be The only flag bits that can be written are and Fibre Channel hosts only support the
       flag.  causes the entry to be permanent.  specifies that the ARP code should respond to ARP requests for the  indicated	host  coming  from
       other  machines.   This	allows	a host to act as an ARP server, which may be useful in convincing an ARP-only machine to talk to a non-ARP
       machine.

       ARP watches passively for hosts impersonating the local host (i.e., a host that responds to an ARP mapping request  for	the  local  host's
       address).

DIAGNOSTICS

       This message printed on the console screen means that
	    ARP has discovered another host on the local network that responds to mapping requests for its own Internet address.

WARNINGS

       To enable the encapsulation method, use the command (see ifconfig(1M)).

AUTHOR

       ARP was developed by the University of California, Berkeley.

SEE ALSO

       ifconfig(1M), inet(3N), lan(7), arp(1M).

       RFC826, Dave Plummer, Network Information Center, SRI.

																	   arp(7P)