- Show current arp table:arp -a- Clear the entire cache:sudo arp -a -d- Delete a specific entry:arp -d [address]- Create an entry:arp -s [address] [mac address]
arp [-vn] [-H type] [-i if] [-ae] [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 privilege 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 table.
arp -s address hw_addr is used to set up a new table entry. The format of the hw_addr parameter is dependent 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 simplify 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.
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.
/usr/sbin/arp -i eth0 -Ds 10.0.0.2 eth1 pub
This will answer ARP requests for 10.0.0.2 on eth0 with the MAC address for eth1.
/usr/sbin/arp -i eth1 -d 10.0.0.1
Delete the ARP table entry for 10.0.0.1 on interface eth1. This will match published proxy ARP entries and permanent entries.
/proc/net/arp /etc/networks /etc/hosts /etc/ethers
rarp(8), route(8), ifconfig(8), netstat(8)
Fred N. van Kempen <firstname.lastname@example.org>, Bernd Eckenfels <email@example.com>.