ARP(8)                                              Linux Programmer's Manual                                             ARP(8)



NAME
       arp - manipulate the system ARP cache


SYNOPSIS
       arp [-evn] [-H type] [-i if] -a [hostname]

       arp [-v] [-i if] -d hostname [pub]

       arp [-v] [-H type] [-i if] -s hostname hw_addr [temp]

       arp [-v] [-H type] [-i if] -s hostname hw_addr [netmask nm] pub

       arp [-v] [-H type] [-i if] -Ds hostname ifa [netmask nm] pub

       arp [-vnD] [-H type] [-i if] -f [filename]


NOTE
       This program is obsolete. For replacement check ip neighbor.


DESCRIPTION
       Arp  manipulates  the  kernel's ARP cache in various ways.  The primary options are clearing an address mapping entry and
       manually setting up one.  For debugging purposes, the arp program also allows a complete dump of the ARP cache.


OPTIONS
       -v, --verbose
              Tell the user what is going on by being verbose.

       -n, --numeric
              shows numerical addresses instead of trying to determine symbolic host, port or user names.

       -H type, --hw-type type, -t type
              When setting or reading the ARP cache, this optional parameter tells arp which class of entries  it  should  check
              for.   The  default  value  of  this  parameter is ether (i.e. hardware code 0x01 for IEEE 802.3 10Mbps Ethernet).
              Other values might include network technologies such as ARCnet (arcnet) ,  PROnet  (pronet)  ,  AX.25  (ax25)  and
              NET/ROM (netrom).

       -a [hostname], --all [hostname]
              Shows  the  entries of the specified hosts.  If the hostname parameter is not used, all entries will be displayed.
              The entries will be displayed in alternate (BSD) style.

       -d hostname, --delete hostname
              Remove any entry for the specified host.  This can be used if the indicated host is brought down, for example.

       -D, --use-device
              Use the interface ifa's hardware address.

       -e     Shows the entries in default (Linux) style.

       -i If, --device If
              Select an interface. When dumping the ARP cache only entries matching the specified  interface  will  be  printed.
              When setting a permanent or temp ARP entry this interface will be associated with the entry; if this option is not
              used, the kernel will guess based on the routing table. For pub entries the specified interface is  the  interface
              on which ARP requests will be answered.

              NOTE: This has to be different from the interface to which the IP datagrams will be routed.

       -s hostname hw_addr, --set hostname
              Manually create an ARP address mapping entry for host hostname with hardware address set to hw_addr class, but for
              most classes one can assume that the usual presentation can be used.  For the Ethernet class, this is 6  bytes  in
              hexadecimal, separated by colons. When adding proxy arp entries (that is those with the publish flag set a netmask
              may be specified to proxy arp for entire subnets. This is not good practice, but is  supported  by  older  kernels
              because it can be useful. If the temp flag is not supplied entries will be permanent stored into the ARP cache.
              NOTE:  As  of  kernel  2.2.0 it is no longer possible to set an ARP entry for an entire subnet. Linux instead does
              automagic proxy arp when a route exists and it is forwarding. See arp(7) for details.

       -f filename, --file filename
              Similar to the -s option, only this time the address info is taken from file filename set up.   The  name  of  the
              data  file is very often /etc/ethers, but this is not official. If no filename is specified /etc/ethers is used as
              default.

              The format of the file is simple; it only contains ASCII text lines with a hardware address and a  hostname  sepa-
              rated by whitespace. Additionally the pub, temp and netmask flags can be used.

       In all places where a hostname is expected, one can also enter an IP address in dotted-decimal notation.

       As a special case for compatibility the order of the hostname and the hardware address can be exchanged.

       Each  complete  entry  in the ARP cache will be marked with the C flag. Permanent entries are marked with M and published
       entries have the P flag.


FILES
       /proc/net/arp,
       /etc/networks
       /etc/hosts
       /etc/ethers


SEE ALSO
       ip(8)


AUTHORS
       Fred N. van Kempen, <waltjeATuwalt.org> with a lot of improvements from  net-tools  Maintainer  Bernd  Eckenfels
       <net-toolsATlina.de>.



net-tools                                                  5 Jan 1999                                                     ARP(8)