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

NAME
     arp - address resolution display and control

SYNOPSIS
     arp [--libxo options] [-n] [-i interface] hostname
     arp [--libxo options] [-n] [-i interface] -a
     arp -d hostname [pub]
     arp -d [-i interface] -a
     arp -s hostname ether_addr [temp] [blackhole | reject] [pub]
     arp -S hostname ether_addr [temp] [blackhole | reject] [pub]
     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
     notation.

     Available options:

     --libxo
             Generate output via libxo(3) in a selection of different human
             and machine readable formats.  See xo_parse_args(3) for details
             on command line arguments.

     -a      The program displays or, if it is used with the -d flag, 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.

             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.

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

     -s hostname ether_addr
             Create an ARP entry for the host called hostname with the
             Ethernet 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 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
             similar 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.

     -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] [blackhole | reject] [pub]

             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.

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

HISTORY
     The arp utility appeared in 4.3BSD.

FreeBSD 13.1-RELEASE-p6          July 13, 2020         FreeBSD 13.1-RELEASE-p6