1.\" $OpenBSD: arp.8,v 1.18 2007/05/31 19:20:22 jmc Exp $ 2.\" $NetBSD: arp.8,v 1.7 1995/03/01 11:50:59 chopps Exp $ 3.\" 4.\" Copyright (c) 1985, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" from: @(#)arp.8 8.1 (Berkeley) 6/6/93 32.\" 33.Dd $Mdocdate: May 31 2007 $ 34.Dt ARP 8 35.Os 36.Sh NAME 37.Nm arp 38.Nd address resolution display and control 39.Sh SYNOPSIS 40.Nm arp 41.Op Fl adn 42.Ar hostname 43.Nm arp 44.Op Fl F 45.Op Fl f Ar file 46.Fl s Ar hostname ether_addr 47.Op Cm temp | permanent 48.Op Cm pub 49.Sh DESCRIPTION 50The 51.Nm 52program displays and modifies the Internet-to-Ethernet address translation 53tables used by the address resolution protocol 54.Pq Xr arp 4 . 55With no flags, the program displays the current 56.Tn ARP 57entry for 58.Ar hostname . 59The host may be specified by name or by number, 60using Internet dot notation. 61.Pp 62Available options: 63.Bl -tag -width Ds 64.It Fl a 65Display all of the current 66.Tn ARP 67entries. 68See also the 69.Fl d 70option below. 71.It Fl d 72Delete an entry for the host called 73.Ar hostname . 74Alternatively, the 75.Fl d 76flag may be combined with the 77.Fl a 78flag to delete all entries, with hostname lookups automatically 79disabled. 80Only the superuser may delete entries. 81.It Fl F 82Force existing entries for the given host to be overwritten 83(only relevant to the 84.Fl f 85and 86.Fl s 87options). 88.It Fl f Ar file 89Process entries from 90.Ar file 91to be set in the 92.Tn ARP 93tables. 94Any entries in the file that already exist for a given host 95will not be overwritten unless 96.Fl F 97is given. 98Entries in the file should be of the form: 99.Bd -filled -offset indent 100.Ar hostname ether_addr 101.Op Cm temp | permanent 102.Op Cm pub 103.Ed 104.Pp 105The entry will be static, i.e., will not time out, unless the word 106.Cm temp 107is given in the command. 108A static 109.Tn ARP 110entry can be overwritten by network traffic, unless the word 111.Cm permanent 112is given. 113If the word 114.Cm pub 115is given, the entry will be 116.Dq published ; 117i.e., this system will 118act as an 119.Tn ARP 120server, 121responding to requests for 122.Ar hostname 123even though the host address is not its own. 124This behavior has traditionally been called 125.Em proxy ARP . 126.It Fl n 127Show network addresses as numbers (normally 128.Nm 129attempts to display addresses symbolically). 130.It Xo 131.Fl s Ar hostname ether_addr 132.Op Cm temp | permanent 133.Op Cm pub 134.Xc 135Create an 136.Tn ARP 137entry for the host called 138.Ar hostname 139with the Ethernet address 140.Ar ether_addr . 141The Ethernet address is given as six hexadecimal bytes separated by 142colons. 143.Pp 144The 145.Cm permanent , pub , 146or 147.Cm temp 148modifiers may be specified with meanings as given above. 149.Pp 150If the entry already exists for the given host, it will not 151be replaced unless 152.Fl F 153is given. 154.El 155.Sh EXAMPLES 156View the current 157.Xr arp 4 158table: 159.Pp 160.Dl $ arp -a 161.Pp 162Create a permanent 163entry (one that cannot be overwritten by other network traffic): 164.Pp 165.Dl # arp -s 10.0.0.2 00:90:27:bb:cc:dd permanent 166.Pp 167Create proxy ARP 168entries on interface fxp0 169(MAC address 00:90:27:bb:cc:dd), 170for IP addresses 204.1.2.3 and 204.1.2.4: 171.Bd -literal -offset indent 172# arp -s 204.1.2.3 00:90:27:bb:cc:dd pub 173# arp -s 204.1.2.4 00:90:27:bb:cc:dd pub 174.Ed 175.Sh SEE ALSO 176.Xr inet 3 , 177.Xr arp 4 , 178.Xr ifconfig 8 179.Sh HISTORY 180The 181.Nm 182command appeared in 183.Bx 4.3 . 184