RARP (Reverse Address Resolution Protocol), is basically a type of protocol with
the help of which the local area network can first request for learning the IP address from the gateways server ARP table or even from the Cache. Firstly a network administrator needs to create the table in the local area networks gateway router which basically maps the physical machine or from the Mac address which corresponds to the internet protocol address. So when a new machine is being setted up, its RARP client program will be requesting from the RARP server on the router which is to be sent to the IP number. If its assumed that the entry has been setted up in the router table, the RARP server will then return the IP address to the machine which will be stored in itself so that it can be used in the future. RARP is mainly available for Ethernet, token ring form of LAN and is also available for FDDI (Fiber Distributed-Data Interface).
RARP mainly maps the ethernet address up to 48 bits and IPv4 address to 32 bits which is basically nothing but just the reverse of the ARP. So, when the RARP on a network is configured o the server, when the hosts are running in the network client mode these obtain their IP addresses automatically and also the information regarding the TCP/IP configuration files from the server. The file in.rarpd daemon enables the RARP services and also RARP makes use of several files with which the map MAC addresses to the IP addresses. So, if you are initiating the in.rarpd daemon tool then first you will need to setup the Ethernet file and then you need to maintain the same file on all the hosts which are running the daemon so that the changes are shown on the network.
RARP is basically the terminology which is used with mainly the 48 bit structure and not with the 32 bit structure. RARP protocol requires one or more than one server hosts so as to maintain a database of mappings for the Link Layer addresses to their respective protocol addresses.