Provided by: net-tools_1.60-16ubuntu2_i386 bug

NAME

       arp - manipulate the system ARP cache

SYNOPSIS

       arp [-vn] [-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]

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
              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], --display [hostname]
              Shows the entries of  the  specified  hosts.   If  the  hostname
              parameter is not used, all entries will be displayed.

       -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.

       -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. Also the dontpub option which is available  for  delete
              and set operations cannot be used with 2.4 and newer kernels.

       -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  hostname,  and  a  hardware address separated 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

       rarp(8), route(8), ifconfig(8), netstat(8)

AUTHORS

       Fred   N.  van  Kempen,  <waltje@uwalt.nl.mugnet.org>  with  a  lot  of
       improvements  from   net-tools   Maintainer   Bernd   Eckenfels   <net-
       tools@lina.inka.de>.