ARP(8) Linux Programmer's Manual ARP(8)
arp - manipulate the system ARP cache
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]
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.
Tell the user what is going on by being verbose.
shows numerical addresses instead of trying to determine symbolic host, port or
-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], --display [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)
-d hostname, --delete hostname
Remove any entry for the specified host. This can be used if the indicated host is
brought down, for example.
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 inter-
face 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
-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 for-
warding. See arp(7) for details.
-f filename, --file filename
Similar to the -s option, only this time the address info is taken from file file-
name 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 host-
name, 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-
As a special case for compatibility the order of the hostname and the hardware address can
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.
rarp(8), route(8), ifconfig(8), netstat(8)
Fred N. van Kempen, <email@example.com> with a lot of improvements from net-tools
Maintainer Bernd Eckenfels <firstname.lastname@example.org>.
net-tools 5 Jan 1999 ARP(8)