---
name: "arp"
section: "8"
platform: "macos"
package: "network_cmds"
version: "741.100.2"
release: "macOS 26.5"
platforms: ["linux", "freebsd", "openbsd", "macos"]
url: "https://new.carta.tech/arp"
---

# arp(8)

address resolution display and control

## NAME

**arp** – address resolution display and control

## SYNOPSIS

**arp** \[**-n**\] \[**-i** *interface*\] *hostname*

**arp** \[**-n**\] \[**-i** *interface*\] \[**-l**\] **-a**

**arp** **-d** *hostname* \[**pub**\] \[**ifscope** **interface**\]

**arp** **-d** \[**-i** *interface*\] **-a**

**arp** **-s** *hostname* *ether\_addr* \[**temp**\] \[**reject**\] \[**blackhole**\] \[**pub** \[**only**\]\] \[**ifscope** **interface**\]

**arp** **-S** *hostname* *ether\_addr* \[**temp**\] \[**reject**\] \[**blackhole**\] \[**pub** \[**only**\]\] \[**ifscope** **interface**\]

**arp** **-f** *filename*

## DESCRIPTION

The **arp** utility displays and modifies the Internet-to-Ethernet address translation tables used by the address resolution protocol ([arp(4)](/arp/4.md)). With no flags, the program displays the current ARP entry for *hostname*. The host may be specified by name or by number, using Internet dot notation.

Available options:

- **-a**

  The program displays or deletes all of the current ARP entries.

- **-d**

  A super-user may delete an entry for the host called *hostname* with the **-d** flag. If the **pub** keyword is specified, only the “published” ARP entry for this host will be deleted. If the **ifscope** keyword is specified, the entry specific to the interface will be deleted.

  Alternatively, the **-d** flag may be combined with the **-a** flag to delete all entries.

- **-i** *interface*

  Limit the operation scope to the ARP entries on *interface*. Applicable only to the following operations: display one, display all, delete all.

- **-l**

  Show link-layer reachability information.

- **-n**

  Show network addresses as numbers (normally **arp** attempts to display addresses symbolically).

- **-s** *hostname* *ether\_addr*

  Create an ARP entry for the host called *hostname* with the Ethernet address *ether\_addr*. The Ethernet address is given as six hex bytes separated by colons. The entry will be permanent unless the word **temp** is given in the command. If the word **pub** is given, the entry will be “published”; i.e., this system will act as an ARP server, responding to requests for *hostname* even though the host address is not its own. In this case the *ether\_addr* can be given as **auto** in which case the interfaces on this host will be examined, and if one of them is found to occupy the same subnet, its Ethernet address will be used. If the **only** keyword is also specified, this will create a “published (proxy only)” entry. This type of entry is created automatically if **arp** detects that a routing table entry for *hostname* already exists.

  If the **reject** keyword is specified the entry will be marked so that traffic to the host will be discarded and the sender will be notified the host is unreachable. The **blackhole** keyword is similar in that traffic is discarded but the sender is not notified. These can be used to block external traffic to a host without using a firewall.

  If the **ifscope** keyword is specified, the entry will set with an additional property that strictly associate the entry to the interface. This allows for the presence of multiple entries with the same destination on different interfaces.

- **-S** *hostname* *ether\_addr*

  Is just like **-s** except any existing ARP entry for this host will be deleted first.

- **-f** *filename*

  Cause the file *filename* 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* \[**temp**\] \[**pub** \[**only**\]\] \[**ifscope** **interface**\]

  with argument meanings as given above. Leading whitespace and empty lines are ignored. A ‘#’ character will mark the rest of the line as a comment.

- **-x**

  Show extended link-layer reachability information in addition to that shown by the **-l** flag.

## SEE ALSO

[inet(3)](/inet/3.md), [arp(4)](/arp/4.md), [ifconfig(8)](/ifconfig/8.md), [ndp(8)](/ndp/8.md)

## HISTORY

The **arp** utility appeared in 4.3BSD.