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Address Resolution Protocol (ARP) display and control


arp hostname
arp -a
arp -d hostname
arp -f filename 
arp -p pathname
arp -n
arp -s hostname ether_addr [pub] [temp]


Display all of the current ARP entries.
-d hostname
Delete an entry for the specified host. Only the superuser can use this option.
-f filename
This option is supported only when using the full stack with builtin ARP support (see the external_arp option of npm-tcpip.so).

The -f option causes the specified file to be read and multiple entries to be set in the ARP tables. Entries in the file should be of the form:

hostname ether_addr [pub] [temp]

with argument meanings as given for option -s.

Show network addresses as numbers. By default, arp attempts to display addresses symbolically.
-p pathname
The path on which to perform operations. The default for pathname is /dev/io-net/ip_en.
-s hostname ether_addr [pub] [temp]
Create an ARP entry for the host hostname with the Ethernet address ether_addr. The Ethernet address is given as six hex bytes separated by colons.

If pub is given, the entry is "published." That is, this system acts as an ARP server, responding to requests for hostname, even though the IP address that's mapped to hostname isn't the address of this system.

The entry is permanent unless the word temp is given in the command.

The name of the local host as defined in the /etc/hosts file.


The arp utility displays and modifies the Internet-to-Ethernet address translation tables used by the Address Resolution Protocol (ARP).

With no options, the utility displays the current ARP entry for hostname. The host may be specified by name or by number, using Internet dot notation.


This utility is based on copyright software of The Regents of the University of California; for the copyright notice, see arp in the appendix Third-Party Copyright Notices.

See also:

ifconfig, npm-tcpip.so

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