---
name: "rarpd"
section: "8"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd", "openbsd", "macos"]
url: "https://new.carta.tech/rarpd"
---

# rarpd(8)

reverse ARP daemon

## NAME

**rarpd** – reverse ARP daemon

## SYNOPSIS

**rarpd** **-a** \[**-dfsv**\] \[**-t** *directory*\] \[**-P** *pidfile*\]

**rarpd** \[**-dfsv**\] \[**-t** *directory*\] \[**-P** *pidfile*\] *interface*

## DESCRIPTION

The **rarpd** utility services Reverse ARP requests on the Ethernet connected to *interface*. Upon receiving a request, **rarpd** maps the target hardware address to an IP address via its name, which must be present in both the [ethers(5)](/ethers/5.md) and [hosts(5)](/hosts/5.md) databases. If a host does not exist in both databases, the translation cannot proceed and a reply will not be sent.

By default, a request is honored only if the server (i.e., the host that **rarpd** is running on) can "boot" the target; that is, a file or directory matching the glob */tftpboot/ipaddr\** exists, where *ipaddr* is the target IP address in hex. For example, the IP address 204.216.27.18 will be replied to if any of */tftpboot/CCD81B12*, */tftpboot/CCD81B12.SUN3*, or */tftpboot/CCD81B12-boot* exist. This requirement can be overridden with the **-s** flag (see below).

In normal operation, **rarpd** forks a copy of itself and runs in the background. Anomalies and errors are reported via [syslog(3)](/syslog/3.md).

The following options are available:

- **-a**

  Listen on all the Ethernets attached to the system. If **-a** is omitted, an interface must be specified.

- **-d**

  If **-f** is also specified, **rarpd** logs messages to *stdout* and *stderr* instead of via [syslog(3)](/syslog/3.md).

- **-f**

  Run in the foreground.

- **-P**

  Specify the pathname of the PID file. If not specified, */var/run/rarpd.pid* or */var/run/rarpd.ifname.pid* will be used depending on the **-a** flag or the specified interface name.

- **-s**

  Supply a response to any RARP request for which an ethernet to IP address mapping exists; do not depend on the existence of */tftpboot/ipaddr\**.

- **-t**

  Supply an alternate tftp root directory to */tftpboot*, similar to the **-s** option of [tftpd(8)](/tftpd/8.md). This permits **rarpd** to selectively respond to RARP requests, but use an alternate directory for IP checking.

- **-v**

  Enable verbose syslogging.

## FILES

- */etc/ethers*

  - */etc/hosts*

  - */tftpboot*

  - */var/run/rarpd.pid*

  ## SEE ALSO

[bpf(4)](/bpf/4.md) Finlayson, R., Mann, T., Mogul, J.C., and Theimer, M., *RFC 903: Reverse Address Resolution Protocol*, June 1984, 4 p.

## AUTHORS

Craig Leres ⟨*leres@ee.lbl.gov*⟩ and Steven McCanne ⟨*mccanne@ee.lbl.gov*⟩. Lawrence Berkeley Laboratory, University of California, Berkeley, CA.

## BUGS

The **rarpd** utility can depend on the DNS to resolve the name discovered from */etc/ethers*. If this name is not in the DNS but is in */etc/hosts*, the DNS lookup can cause a delayed RARP response, so in this situation it is recommended to configure [nsswitch.conf(5)](/nsswitch.conf/5.md) to read */etc/hosts* first.