RARP configuration Some network units (computers, terminals) store their own networking information on other machines. When these machines boot, they have no idea what their own IP number(s) is/are. They can barely communicate on the network because of this lack of identity. The RARP protocol is one of the few protocols (BOOTP and DHCP are other ones) which solve this dilemma. 11.. PPrriinncciippllee When a configuration device boots, it sends a broadcast using the RARP protocol (Reverse Address Resolution Protocol). Mostly, it says: Well, here I am. Here is a small message from me. From this message you should get my ethernet MAC address (6 hex digits uniquely identifying any Ethernet adapter ever built). From my MAC address, someone should be able to tell me my primary IP number. Thanks!:) One _L_i_n_u_x server may act as a RARP server. It will answer such a query only if it knows the answer. 22.. TTaasskk To define a RARP server, you must enter pairs of MAC addresses and IP numbers. You can also enter host names (defined in /etc/hosts or in a DNS server). The kernel must be compiled with RARP support (either built-in or as a module). Linuxconf will inform you if your configuration is not suitable (no built-in, no module). 33.. DDiiaalloogg ffiieellddss Here are the four fields you have to fill for each RARP entry: 33..11.. TThhiiss rreeccoorrdd iiss aaccttiivvee You can comment out a record using this checkbox. Many RARP clients assume that if your server answers a RARP query, it can provide more boot services for this client. Diskless Linux workstation works this way. If your server does not provide such a service at one point in time, you are better off disabling the entry. Note that several servers may process RARP queries on the same network without problems. 33..22.. HHoosstt nnaammee oorr IIPP nnuummbbeerr Enter a host name that is either defined in /etc/hosts (see the menu "information about other hosts" in the Networking sub-menu of Linuxconf) or in a DNS. Or just enter a plain IP number (x.y.z.w). 33..33.. EEtthheerrnneett aaddddrreessss ((tthhee MMAACC aaddddrreessss)) The MAC address is a six-field hexadecimal number generally presented like this: 00:11:22:33:44:55 You can obtain this number different ways. Here are some: 33..33..11.. LLiinnuuxx ttaallkkss _L_i_n_u_x displays its MAC number when it boots. You can simply boot a configuration-less Linux computer and watch it print its MAC number to the screen. You will have plenty of time to write it down, since it won't boot much further than that, until a RARP server responds to its query. Examples: diskless NFS-rooted Linux workstations and X terminals come to mind as configurationless Linux devices using (optionally) RARP to identify themselves. 33..33..22.. TThhee aaddaapptteerr ccoonnffiigguurraattiioonn pprrooggrraamm Most Ethernet devices (all?) come with a _D_O_S program allowing one to configure the device. This program prints the MAC number. 33..33..33.. UUssee ttccppdduummpp The Linux utility tcpdump can _s_p_y on the network and report on any packets going by. Tcpdump is quite handy for getting those "annoying to type" MAC numbers. Just execute: tcpdump rarp Boot the device and watch it there. Cut and paste the number into Linuxconf's dialog, add a name or an IP number and let Linuxconf activate the configuration. Watch the device complete its boot process successfully. Automating this mechanism is on the TO-DO list for Linuxconf. 33..44.. CCoommmmeenntt Put whatever you want here. Maybe just a reminder for why you disabled the entry.