1.\" Copyright (c) 1985, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 4. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)arp.8 8.1 (Berkeley) 6/6/93 29.\" $FreeBSD$ 30.\" 31.Dd March 18, 2008 32.Dt ARP 8 33.Os 34.Sh NAME 35.Nm arp 36.Nd address resolution display and control 37.Sh SYNOPSIS 38.Nm 39.Op Fl n 40.Op Fl i Ar interface 41.Ar hostname 42.Nm 43.Op Fl n 44.Op Fl i Ar interface 45.Fl a 46.Nm 47.Fl d Ar hostname 48.Op Cm pub 49.Nm 50.Fl d 51.Op Fl i Ar interface 52.Fl a 53.Nm 54.Fl s Ar hostname ether_addr 55.Op Cm temp 56.Op Cm reject 57.Op Cm blackhole 58.Op Cm pub Op Cm only 59.Nm 60.Fl S Ar hostname ether_addr 61.Op Cm temp 62.Op Cm reject 63.Op Cm blackhole 64.Op Cm pub Op Cm only 65.Nm 66.Fl f Ar filename 67.Sh DESCRIPTION 68The 69.Nm 70utility displays and modifies the Internet-to-Ethernet address translation 71tables used by the address resolution protocol 72.Pq Xr arp 4 . 73With no flags, the program displays the current 74.Tn ARP 75entry for 76.Ar hostname . 77The host may be specified by name or by number, 78using Internet dot notation. 79.Pp 80Available options: 81.Bl -tag -width indent 82.It Fl a 83The program displays or deletes all of the current 84.Tn ARP 85entries. 86.It Fl d 87A super-user may delete an entry for the host called 88.Ar hostname 89with the 90.Fl d 91flag. 92If the 93.Cm pub 94keyword is specified, only the 95.Dq published 96.Tn ARP 97entry 98for this host will be deleted. 99.Pp 100Alternatively, the 101.Fl d 102flag may be combined with the 103.Fl a 104flag to delete all entries. 105.It Fl i Ar interface 106Limit the operation scope to the 107.Tn ARP 108entries on 109.Ar interface . 110Applicable only to the following operations: 111display one, display all, delete all. 112.It Fl n 113Show network addresses as numbers (normally 114.Nm 115attempts to display addresses symbolically). 116.It Fl s Ar hostname ether_addr 117Create an 118.Tn ARP 119entry for the host called 120.Ar hostname 121with the Ethernet address 122.Ar ether_addr . 123The Ethernet address is given as six hex bytes separated by colons. 124The entry will be permanent unless the word 125.Cm temp 126is given in the command. 127If the word 128.Cm pub 129is given, the entry will be 130.Dq published ; 131i.e., this system will 132act as an 133.Tn ARP 134server, 135responding to requests for 136.Ar hostname 137even though the host address is not its own. 138In this case the 139.Ar ether_addr 140can be given as 141.Cm auto 142in which case the interfaces on this host will be examined, 143and if one of them is found to occupy the same subnet, its 144Ethernet address will be used. 145If the 146.Cm only 147keyword is also specified, this will create a 148.Dq "published (proxy only)" 149entry. 150This type of entry is created automatically if 151.Nm 152detects that a routing table entry for 153.Ar hostname 154already exists. 155.Pp 156If the 157.Cm reject 158keyword is specified the entry will be marked so that traffic to 159the host will be discarded and the sender will be notified the 160host is unreachable. 161The 162.Cm blackhole 163keyword is similar in that traffic is discarded but the sender is 164not notified. 165These can be used to block external traffic to a host without 166using a firewall. 167.It Fl S Ar hostname ether_addr 168Is just like 169.Fl s 170except any existing 171.Tn ARP 172entry for this host will be deleted first. 173.It Fl f Ar filename 174Cause the file 175.Ar filename 176to be read and multiple entries to be set in the 177.Tn ARP 178tables. 179Entries 180in the file should be of the form 181.Pp 182.Bd -ragged -offset indent -compact 183.Ar hostname ether_addr 184.Op Cm temp 185.Op Cm pub 186.Ed 187.Pp 188with argument meanings as given above. 189Leading whitespace and empty lines are ignored. 190A 191.Ql # 192character will mark the rest of the line as a comment. 193.El 194.Sh SEE ALSO 195.Xr inet 3 , 196.Xr arp 4 , 197.Xr ifconfig 8 198.Sh HISTORY 199The 200.Nm 201utility appeared in 202.Bx 4.3 . 203