Linux Programmer’s Manual
arp − manipulate the system ARP cache
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 ifname [netmask nm] pub
arp [−vnD] [−H type] [−i if ] −f [ filename]
Arp manipulates or displays the kernel’s IPv4 network neighbour cache. It can add entries to the table,
delete one or display the current content.
ARP stands for Address Resolution Protocol, which is used to find the media access control address of a
network neighbour for a given IPv4 Address.
arp with no mode specifier will print the current content of the table. It is possible to limit the number of
entries printed, by specifying an hardware address type, interface name or host address.
arp -d address will delete a ARP table entry. Root or netadmin priveledge is required to do this. The entry
is found by IP address. If a hostname is given, it will be resolved before looking up the entry in the ARP ta-
arp -s address hw_addr is used to set up a new table entry. The format of the hw_addr parameter is depen-
dent on the hardware 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. To simplyfy setting up entries for one of your own
network interfaces, you can use the arp −Ds address ifname form. In that case the hardware address is
taken from the interface with the specified name.
Tell the user what is going on by being verbose.
shows numerical addresses i