arp(8) System Manager's Manual arp(8)
NAME
arp - Displays and controls Address Resolution Protocol (ARP) tables
SYNOPSIS
/usr/sbin/arp [-u] [-n] hostname
arp -a [-u] [-n] [-i] [system]
arp -d hostname
arp -f filename
arp -g hostname
arp -s [-u] hostname hardware_addr [temp] [pub] [trail]
FLAGS
Displays all of the current ARP entries. Deletes the entry for hostname if the user issuing the command has superuser authority. Reads
entries from filename and adds those entries to the ARP tables. Use of this flag requires superuser privilege. Entries in the file have
the following format:
hostname hardware_addr [temp] [pub] [trail]
Fields in this format are as follows: Specifies the remote host identified by the entry. Specifies the hardware address of the
remote host. The address is given as 6 hexadecimal bytes separated by colons. Specifies that this ARP table entry is temporary.
When this argument is not used, the table entry is permanent. Indicates that the table entry will be published and that the current
system will act as an ARP server, responding to requests for hostname even though the host address is not its own. Indicates that
the trailer encapsulation may be sent to this host. Sends a gratuitous ARP packet. The hostname can be a local host name, alias,
or IP address. Displays the interface with which the ARP entry is associated. Displays numeric IP addresses and hardware addresses
only. When this flag is not specified, arp displays hostnames, numeric IP addresses, and hardware addresses. Creates a single ARP
entry for hostname. Use of this flag requires superuser privilege. The arguments are explained in the discussion of the -f flag.
Displays the MAC address in noncanonical form with address bytes reversed and separated by a colon character (:). By default, all
addresses are displayed in canonical form with address bytes separated by the hyphen character (-).
When used with the -s flag, this indicates that the hardware_addr is in noncanonical form.
DESCRIPTION
The arp command displays or modifies the current ARP entry for the host specified by hostname. The host may be specified by name or num-
ber, using Internet dot notation.
With no flags, the program displays the current ARP entry for hostname.
The ARP tables can be displayed by any user, but only the superuser can modify them.
EXAMPLES
To display the ARP address-mapping tables for the local host, enter:
arp -a
alpha1.dec.com (16.181.20.2) at 08-00-2b-2c-f5-31 alpha2.dec.com (16.100.21.20) at 08-00-2b-3c-2d-fd To display the ARP address-map-
ping tables for the local host and the interface, enter:
arp -a -i
jupiter (192.45.20.2) at 08-00-2b-1a-f8-23 (tu0) sigma (204.126.98.16) at 08-00-2b-5f-1d-33 (tu1) To add a single entry for the
remote host laszlo to the ARP mapping tables temporarily, enter:
arp -s laszlo 08:00:2b:0f:44:23 temp
The address is considered canonical even though the bytes are separated by colons. For input, the arp command does not use the colon
(:) and hyphen (-) characters to indicate whether the address is canonical or noncanonical.
Note that you must have superuser authority to execute this command. To add a single entry for the remote host laszlo to the ARP
mapping tables temporarily, enter:
arp -u -s laszlo 10:00:d4:f0:22:c4 temp
The -u flag indicates the address is noncanonical. Note that you must have superuser authority to execute this command. To add mul-
tiple entries to the ARP mapping tables from the file newentries, enter:
arp -f newentries
Note that you must have superuser authority to execute this command.
FILES
Specifies the command path.
RELATED INFORMATION
Commands: netstat(1), ifconfig(8)
Protocols: arp(7)
Specifications: RFC 826 delim off
arp(8)