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arp(8)								       arp(8)



NAME

  arp -	Displays and controls Address Resolution Protocol (ARP)	tables

SYNOPSIS

  /usr/sbin/arp	[-u] [-n] hostname

  arp [-a] [-u]	[-n] [-i] system

  arp [-D] hostname

  arp [-d] hostname

  arp [-E] hostname

  arp [-f] filename

  arp [-g] hostname

  arp [-s] [-u]	[hostname] [hardware_addr] [temp] [pub]	[trail]

OPTIONS

  -a  Displays all of the current ARP entries.

  -D hostname
      Disables ARP for hostname. The hostname can be a local host name,
      alias, or	IP address. If you use this option, the	system will no longer
      respond to ARP requests for this IP address. This	might cause network
      connectivity problems with remote	systems. Use of	this option requires
      superuser	privilege.

  -d hostname
      Deletes the entry	for hostname if	the user issuing the command has
      superuser	authority.

  -E hostname
      Enables ARP for hostname.	The hostname can be a local host name, alias,
      or IP address. By	default, the system responds to	ARP requests for all
      local IP addresses. You can use this option to enable ARP	for a host-
      name that	you previously disabled	with the -D option. Use	of this
      option requires superuser	privilege.

  -f filename
      Reads entries from filename and adds those entries to the	ARP tables.
      Use of this option requires superuser privilege.	Entries	in the file
      have the following format:
	   hostname hardware_addr [temp] [pub] [trail]

      Fields in	this format are	as follows:

  hostname
      Specifies	the remote host	identified by the entry.

  hardware_addr
      Specifies	the hardware address of	the remote host. The address format
      is 6 hexadecimal bytes separated by colons; for example,
      xx:xx:xx:xx:xx:xx.

  temp
      Specifies	that this ARP table entry is temporary.	When this argument is
      not used,	the table entry	is permanent.

  pub Indicates	that the table entry will be published and that	the current
      system will act as an ARP	server,	responding to requests for hostname
      even though the host address is not its own.

  trail
      Indicates	that the trailer encapsulation may be sent to this host.

  -g hostname
      Sends a gratuitous ARP packet.  The hostname can be a local host name,
      alias, or	IP address.

  -i  Displays the interface with which	the ARP	entry is associated.

  -n  Displays numeric IP addresses and	hardware addresses only.  When this
      option is	not specified, arp displays hostnames, numeric IP addresses,
      and hardware addresses.

  -s hostname hardware_addr [temp] [pub] [trail]
      Creates a	single ARP entry for hostname. Use of this option requires
      superuser	privilege. The arguments are explained in the discussion of
      the -f option.

  [-u]
      Displays the MAC address in noncanonical form with address bytes
      reversed and separated by	a colon	character (:). By default, all
      addresses	are displayed in canonical form	with address bytes separated
      by the hyphen character (-).

      When used	with the -s option, this indicates that	the hardware_addr is
      in noncanonical form.

DESCRIPTION

  The arp command displays or modifies the current ARP entry for the host
  specified by hostname. The host may be specified by name or number, using
  Internet dot notation.

  With no options, the program displays	the current ARP	entry for hostname.

  The ARP tables can be	displayed by any user, but only	the superuser can
  modify them.

EXAMPLES

   1.  To display the ARP address-mapping tables for the local host, enter:
	    arp	-a

	    alpha1.dec.com (16.181.20.2) at 08-00-2b-2c-f5-31
	    alpha2.dec.com (16.100.21.20) at 08-00-2b-3c-2d-fd

   2.  To display the ARP address-mapping tables for the local host and	the
       interface, enter:
	    arp	-a -i

	    jupiter (192.45.20.2) at 08-00-2b-1a-f8-23 (tu0)
	    sigma (204.126.98.16) at 08-00-2b-5f-1d-33 (tu1)

   3.  To add a	single entry for the remote host laszlo	to the ARP mapping
       tables temporarily, enter:
	    arp	-s laszlo 08:00:2b:0f:44:23 temp

       The address is considered canonical even	though the bytes are
       separated by colons. For	input, the arp command does not	use the	colon
       (:) and hyphen (-) characters to	indicate whether the address is
       canonical or noncanonical.

       Note that you must have superuser authority to execute this command.

   4.  To add a	single entry for the remote host laszlo	to the ARP mapping
       tables temporarily, enter:
	    arp	-u -s laszlo 10:00:d4:f0:22:c4 temp

       The -u option indicates the address is noncanonical. Note that you
       must have superuser authority to	execute	this command.

   5.  To add multiple entries to the ARP mapping tables from the file newen-
       tries, enter:
	    arp	-f newentries

       Note that you must have superuser authority to execute this command.

FILES

  /usr/sbin/arp
      Specifies	the command path.

SEE ALSO

  Commands: netstat(1),	ifconfig(8)

  Protocols: arp(7)

  Specifications:  RFC 826