.\" Copyright (c) 1985, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)arp.8 8.1 (Berkeley) 6/6/93 .\" $FreeBSD: src/usr.sbin/arp/arp.8,v 126.96.36.199 2008/04/25 16:38:14 sam Exp $ .\" .Dd March 18, 2008 .Dt ARP 8 .Os .Sh NAME .Nm arp .Nd address resolution display and control .Sh SYNOPSIS .Nm .Op Fl n .Op Fl i Ar interface .Ar hostname .Nm .Op Fl n .Op Fl i Ar interface .Fl a .Nm .Fl d Ar hostname .Op Cm pub .Op Cm ifscope interface .Nm .Fl d .Op Fl i Ar interface .Fl a .Nm .Fl s Ar hostname ether_addr .Op Cm temp .Op Cm reject .Op Cm blackhole .Op Cm pub Op Cm only .Op Cm ifscope interface .Nm .Fl S Ar hostname ether_addr .Op Cm temp .Op Cm reject .Op Cm blackhole .Op Cm pub Op Cm only .Op Cm ifscope interface .Nm .Fl f Ar filename .Sh DESCRIPTION The .Nm utility displays and modifies the Internet-to-Ethernet address translation tables used by the address resolution protocol .Pq Xr arp 4 . With no flags, the program displays the current .Tn ARP entry for .Ar hostname . The host may be specified by name or by number, using Internet dot notation. .Pp Available options: .Bl -tag -width indent .It Fl a The program displays or deletes all of the current .Tn ARP entries. .It Fl d A super-user may delete an entry for the host called .Ar hostname with the .Fl d flag. If the .Cm pub keyword is specified, only the .Dq published .Tn ARP entry for this host will be deleted. If the .Cm ifscope keyword is specified, the entry specific to the interface will be deleted. .Pp Alternatively, the .Fl d flag may be combined with the .Fl a flag to delete all entries. .It Fl i Ar interface Limit the operation scope to the .Tn ARP entries on .Ar interface . Applicable only to the following operations: display one, display all, delete all. .It Fl n Show network addresses as numbers (normally .Nm attempts to display addresses symbolically). .It Fl s Ar hostname ether_addr Create an .Tn ARP entry for the host called .Ar hostname with the Ethernet address .Ar ether_addr . The Ethernet address is given as six hex bytes separated by colons. The entry will be permanent unless the word .Cm temp is given in the command. If the word .Cm pub is given, the entry will be .Dq published ; i.e., this system will act as an .Tn ARP server, responding to requests for .Ar hostname even though the host address is not its own. In this case the .Ar ether_addr can be given as .Cm 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 .Cm only keyword is also specified, this will create a .Dq "published (proxy only)" entry. This type of entry is created automatically if .Nm detects that a routing table entry for .Ar hostname already exists. .Pp If the .Cm 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 .Cm 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. .Pp If the .Cm 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. .It Fl S Ar hostname ether_addr Is just like .Fl s except any existing .Tn ARP entry for this host will be deleted first. .It Fl f Ar filename Cause the file .Ar filename to be read and multiple entries to be set in the .Tn ARP tables. Entries in the file should be of the form .Pp .Bd -ragged -offset indent -compact .Ar hostname ether_addr .Op Cm temp .Op Cm pub Op Cm only .Op Cm ifscope interface .Ed .Pp with argument meanings as given above. Leading whitespace and empty lines are ignored. A .Ql # character will mark the rest of the line as a comment. .El .Sh SEE ALSO .Xr inet 3 , .Xr arp 4 , .Xr ifconfig 8 .Sh HISTORY The .Nm utility appeared in .Bx 4.3 .