ARP(8)                    BSD System Manager's Manual                   ARP(8)

NAME
     arp -- address resolution display and control

SYNOPSIS
     arp [-n] [-i interface] hostname
     arp [-n] [-i interface] [-l] -a
     arp -d hostname [pub] [ifscope interface]
     arp -d [-i interface] -a
     arp -s hostname ether_addr [temp] [reject] [blackhole] [pub [only]]
         [ifscope interface]
     arp -S hostname ether_addr [temp] [reject] [blackhole] [pub [only]]
         [ifscope interface]
     arp -f filename

DESCRIPTION
     The arp utility displays and modifies the Internet-to-Ethernet address
     translation tables used by the address resolution protocol (arp(4)).
     With no flags, the program displays the current ARP entry for hostname.
     The host may be specified by name or by number, using Internet dot nota-
     tion.

     Available options:

     -a      The program displays or deletes all of the current ARP entries.

     -d      A super-user may delete an entry for the host called hostname
             with the -d flag.  If the pub keyword is specified, only the
             ``published'' ARP entry for this host will be deleted.  If the
             ifscope keyword is specified, the entry specific to the interface
             will be deleted.

             Alternatively, the -d flag may be combined with the -a flag to
             delete all entries.

     -i interface
             Limit the operation scope to the ARP entries on interface.
             Applicable only to the following operations: display one, display
             all, delete all.

     -l      Show link-layer reachability information.

     -n      Show network addresses as numbers (normally arp attempts to dis-
             play addresses symbolically).

     -s hostname ether_addr
             Create an ARP entry for the host called hostname with the Ether-
             net address ether_addr.  The Ethernet address is given as six hex
             bytes separated by colons.  The entry will be permanent unless
             the word temp is given in the command.  If the word pub is given,
             the entry will be ``published''; i.e., this system will act as an
             ARP server, responding to requests for hostname even though the
             host address is not its own.  In this case the ether_addr can be
             given as auto in which case the interfaces on this host will be
             examined, and if one of them is found to occupy the same subnet,
             its Ethernet address will be used.  If the only keyword is also
             specified, this will create a ``published (proxy only)'' entry.
             This type of entry is created automatically if arp detects that a
             routing table entry for hostname already exists.

             If the reject keyword is specified the entry will be marked so
             that traffic to the host will be discarded and the sender will be
             notified the host is unreachable.  The blackhole keyword is simi-
             lar in that traffic is discarded but the sender is not notified.
             These can be used to block external traffic to a host without
             using a firewall.

             If the ifscope keyword is specified, the entry will set with an
             additional property that strictly associate the entry to the
             interface. This allows for the presence of mutiple entries with
             the same destination on different interfaces.

     -S hostname ether_addr
             Is just like -s except any existing ARP entry for this host will
             be deleted first.

     -f filename
             Cause the file filename to be read and multiple entries to be set
             in the ARP tables.  Entries in the file should be of the form

                   hostname ether_addr [temp] [pub [only]] [ifscope interface]

             with argument meanings as given above.  Leading whitespace and
             empty lines are ignored.  A `#' character will mark the rest of
             the line as a comment.

     -x      Show extended link-layer reachability information in addition to
             that shown by the -l flag.

SEE ALSO
     inet(3), arp(4), ifconfig(8), ndp(8)

HISTORY
     The arp utility appeared in 4.3BSD.

BSD                             March 18, 2008                             BSD