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RARP(8) Linux Programmer's Manual RARP(8)


rarpd - Reverse Address Resolution Protocol (RARP) daemon


rarpd [-aAvode] [-b bootdir] [interface]


Rarpd is a daemon which responds to RARP requests. RARP is used by some machines at boot time to discover their IP address. They provide their Ethernet address and rarpd responds with their IP address if it finds it in the ethers database (either /etc/ethers file or NIS+ lookup) and using DNS lookup if the ethers database contains a hostname and not an IP address. In addition, /etc/hosts will provide further means of pairing an IP address to a hostname, in the standard fashion.

By default rarpd also checks if a bootable image, of a name starting with the IP address in hexadecimal upper-case letters, is present in the TFTP boot directory before it decides whether to respond to the RARP request. The comparison involves exactly the first eight characters, and ignores any additional character. A file name shorter than eight characters in length is unsuccessful. Typically, would correspond to an image named like C0A8007A.SUN.

The optional argument interface restricts the daemon instance to access only the indicated network interface. Only a single name is possible.


Do not bind to a single interface, but listen at all configured interfaces.
Respond to reverse requests received as ARP-packets, in addition to those protocol conformant requests transmitted as RARP-packets. See the notes for the background.
Tell the user what is going on by being verbose.
Debugging mode. Do not detach from the tty. This also implies verbose mode.
Skip the check for bootable images in the TFTP boot directory. In the absence of this switch, even if the Ethernet address is present in the ethers database, the lack of a bootable image for the resolved IP will make rarpd refrain from responding to requests for this particular address.
Accept offlink packages on the active interfaces.
Access bootdir instead of the default /tftpboot as the TFTP boot directory for bootable image checks.


This daemon rarpd obsoletes kernel rarp daemon present in Linux kernels up to 2.2 which was controlled by the rarp(8) command.


Renew the internal address list, which records IPv4 addresses available at each active network interface. The restriction set by the command line argument interface is still in effect, if in use.


The protocol stipulates that Reverse Requests be broadcast as RARP packets, using a protocol number different from that in use by ARP packets. However, there has been an obsolete practice of transmitting also Reverse Requests in ARP packets, and some old clients may still be around that adhere to that practice. To activate support for such obsolete client hosts, the switch -A must be applied. Observe, however, that only ARP-packaged ARPOP_RREQUEST messages are added to the servers responsabilities with the use of this option, and that the replies to these will be sent as ARP-packaged ARPOP_RREPLY messages.


Text data base of ethernet to host pairs.
Text lookup table of host names.
Name resolver configuration.
Default boot directory.
Typical name of a boot image. It is a file or a directory. The IPv4 address is translated as eight upper-case, hexadecimal digits in the mandatory part HEXADDR. Optionally, the name may be extended with an arbitrary suffix.


ethers(5), hosts(5), nsswitch.conf(5)


Alexey Kuznetsov, <>
Jakub Jelinek, <>

7 April 2000 rarpd