On Linux operating systems, the arp command 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 address of a network neighbor for a given IPv4 address.

Installing arp

Arp is part of the net-tools package. For example, on systems that use APT for package management, it can be installed with apt-get:

  • Installing arp
  • Syntax
  • Examples
  • Related commands
  • Linux commands help

sudo apt-get update && sudo apt-get install net-tools

Syntax

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]

Modes

arp with no mode specifier prints the current content of the table. It is possible to limit the number of entries printed, by specifying a hardware address type, interface name or host address.

arp -d address deletes an ARP table entry. Root 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.

The command:

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 (“pub”) 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 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.

Options

Notes

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.

Examples

arp

Display network card and Ethernet connectivity.

ifconfig — View or modify the configuration of network interfaces.ip — Display and manipulate information about routing, devices, policy routing and tunnels.netstat — Print information about network connections, routing tables, and more.route — Display and manipulate the IP routing table.