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.\" 3. 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 April 6, 2017 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 -libxo Ar options 40.Op Fl n 41.Op Fl i Ar interface 42.Ar hostname 43.Nm 44.Op Fl -libxo Ar options 45.Op Fl n 46.Op Fl i Ar interface 47.Fl a 48.Nm 49.Fl d Ar hostname 50.Op Cm pub 51.Nm 52.Fl d 53.Op Fl i Ar interface 54.Fl a 55.Nm 56.Fl s Ar hostname ether_addr 57.Op Cm temp 58.Op Cm blackhole No \&| Cm reject 59.Op Cm pub 60.Nm 61.Fl S Ar hostname ether_addr 62.Op Cm temp 63.Op Cm blackhole No \&| Cm reject 64.Op Cm pub 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 -libxo 83Generate output via 84.Xr libxo 3 85in a selection of different human and machine readable formats. 86See 87.Xr xo_parse_args 3 88for details on command line arguments. 89.It Fl a 90The program displays or deletes all of the current 91.Tn ARP 92entries. 93.It Fl d 94A super-user may delete an entry for the host called 95.Ar hostname 96with the 97.Fl d 98flag. 99If the 100.Cm pub 101keyword is specified, only the 102.Dq published 103.Tn ARP 104entry 105for this host will be deleted. 106.Pp 107Alternatively, the 108.Fl d 109flag may be combined with the 110.Fl a 111flag to delete all entries. 112.It Fl i Ar interface 113Limit the operation scope to the 114.Tn ARP 115entries on 116.Ar interface . 117Applicable only to the following operations: 118display one, display all, delete all. 119.It Fl n 120Show network addresses as numbers (normally 121.Nm 122attempts to display addresses symbolically). 123.It Fl s Ar hostname ether_addr 124Create an 125.Tn ARP 126entry for the host called 127.Ar hostname 128with the Ethernet address 129.Ar ether_addr . 130The Ethernet address is given as six hex bytes separated by colons. 131The entry will be permanent unless the word 132.Cm temp 133is given in the command. 134If the word 135.Cm pub 136is given, the entry will be 137.Dq published ; 138i.e., this system will 139act as an 140.Tn ARP 141server, 142responding to requests for 143.Ar hostname 144even though the host address is not its own. 145In this case the 146.Ar ether_addr 147can be given as 148.Cm auto 149in which case the interfaces on this host will be examined, 150and if one of them is found to occupy the same subnet, its 151Ethernet address will be used. 152.Pp 153If the 154.Cm reject 155keyword is specified the entry will be marked so that traffic to 156the host will be discarded and the sender will be notified the 157host is unreachable. 158The 159.Cm blackhole 160keyword is similar in that traffic is discarded but the sender is 161not notified. 162These can be used to block external traffic to a host without 163using a firewall. 164.It Fl S Ar hostname ether_addr 165Is just like 166.Fl s 167except any existing 168.Tn ARP 169entry for this host will be deleted first. 170.It Fl f Ar filename 171Cause the file 172.Ar filename 173to be read and multiple entries to be set in the 174.Tn ARP 175tables. 176Entries 177in the file should be of the form 178.Pp 179.Bd -ragged -offset indent -compact 180.Ar hostname ether_addr 181.Op Cm temp 182.Op Cm blackhole No \&| Cm reject 183.Op Cm pub 184.Ed 185.Pp 186with argument meanings as given above. 187Leading whitespace and empty lines are ignored. 188A 189.Ql # 190character will mark the rest of the line as a comment. 191.El 192.Sh SEE ALSO 193.Xr inet 3 , 194.Xr libxo 3 , 195.Xr xo_parse_args 3 , 196.Xr arp 4 , 197.Xr ifconfig 8 , 198.Xr ndp 8 199.Sh HISTORY 200The 201.Nm 202utility appeared in 203.Bx 4.3 . 204