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 December 25, 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 blackhole No \&| Cm reject 57.Op Cm pub Op Cm only 58.Nm 59.Fl S Ar hostname ether_addr 60.Op Cm temp 61.Op Cm blackhole No \&| Cm reject 62.Op Cm pub Op Cm only 63.Nm 64.Fl f Ar filename 65.Sh DESCRIPTION 66The 67.Nm 68utility displays and modifies the Internet-to-Ethernet address translation 69tables used by the address resolution protocol 70.Pq Xr arp 4 . 71With no flags, the program displays the current 72.Tn ARP 73entry for 74.Ar hostname . 75The host may be specified by name or by number, 76using Internet dot notation. 77.Pp 78Available options: 79.Bl -tag -width indent 80.It Fl a 81The program displays or deletes all of the current 82.Tn ARP 83entries. 84.It Fl d 85A super-user may delete an entry for the host called 86.Ar hostname 87with the 88.Fl d 89flag. 90If the 91.Cm pub 92keyword is specified, only the 93.Dq published 94.Tn ARP 95entry 96for this host will be deleted. 97.Pp 98Alternatively, the 99.Fl d 100flag may be combined with the 101.Fl a 102flag to delete all entries. 103.It Fl i Ar interface 104Limit the operation scope to the 105.Tn ARP 106entries on 107.Ar interface . 108Applicable only to the following operations: 109display one, display all, delete all. 110.It Fl n 111Show network addresses as numbers (normally 112.Nm 113attempts to display addresses symbolically). 114.It Fl s Ar hostname ether_addr 115Create an 116.Tn ARP 117entry for the host called 118.Ar hostname 119with the Ethernet address 120.Ar ether_addr . 121The Ethernet address is given as six hex bytes separated by colons. 122The entry will be permanent unless the word 123.Cm temp 124is given in the command. 125If the word 126.Cm pub 127is given, the entry will be 128.Dq published ; 129i.e., this system will 130act as an 131.Tn ARP 132server, 133responding to requests for 134.Ar hostname 135even though the host address is not its own. 136In this case the 137.Ar ether_addr 138can be given as 139.Cm auto 140in which case the interfaces on this host will be examined, 141and if one of them is found to occupy the same subnet, its 142Ethernet address will be used. 143If the 144.Cm only 145keyword is also specified, this will create a 146.Dq "published (proxy only)" 147entry. 148This type of entry is created automatically if 149.Nm 150detects that a routing table entry for 151.Ar hostname 152already exists. 153.Pp 154If the 155.Cm reject 156keyword is specified the entry will be marked so that traffic to 157the host will be discarded and the sender will be notified the 158host is unreachable. 159The 160.Cm blackhole 161keyword is similar in that traffic is discarded but the sender is 162not notified. 163These can be used to block external traffic to a host without 164using a firewall. 165.It Fl S Ar hostname ether_addr 166Is just like 167.Fl s 168except any existing 169.Tn ARP 170entry for this host will be deleted first. 171.It Fl f Ar filename 172Cause the file 173.Ar filename 174to be read and multiple entries to be set in the 175.Tn ARP 176tables. 177Entries 178in the file should be of the form 179.Pp 180.Bd -ragged -offset indent -compact 181.Ar hostname ether_addr 182.Op Cm temp 183.Op Cm blackhole No \&| Cm reject 184.Op Cm pub Op Cm only 185.Ed 186.Pp 187with argument meanings as given above. 188Leading whitespace and empty lines are ignored. 189A 190.Ql # 191character will mark the rest of the line as a comment. 192.El 193.Sh SEE ALSO 194.Xr inet 3 , 195.Xr arp 4 , 196.Xr ifconfig 8 , 197.Xr ndp 8 198.Sh HISTORY 199The 200.Nm 201utility appeared in 202.Bx 4.3 . 203