Configuring the OkiLAN 6200e IP Address with RARP
RARP is an acronym for Reverse Address Resolution Protocol. Every TCP/IP network device must have a unique 32-bit IP address. TCP/IP network devices will have both an IP address and a 48-bit Ethernet (network hardware) address. Ethernet addresses usually cannot be configured and are hard coded by the manufacturer of the device. RARP is a protocol used by devices that know their network hardware address, but do not know their IP address. When powering up on a network, a device that uses RARP will broadcast its network hardware address in a RARP request message. A RARP server (which may be a UNIX workstation) will respond with an IP address. The device will then know its IP address and use this address to perform subsequent TCP/IP transactions.
Note: Once the OkiLAN 6200e has been assigned an IP address, the OkiLAN 6200e configuration utility (which is accessed by telneting to the OkiLAN 6200e) or OkiNet for TCP/IP will allow you to change and/or make the IP address permanent. This means that a RARP server needs to be available only during installation of the OkiLAN 6200e.
Network hardware addresses are 48-bits and are expressed in 6 bytes in hexadecimal format usually separated by colons. Each hexadecimal byte has a range from 00 to FF.
IP addresses are 32-bits and are expressed in 4 bytes in decimal format usually separated by periods. Each decimal byte has a range from 0 to 255.
The purpose of RARP is to look up a 32-bit IP address given a 48-bit network hardware address. The RARP server (which is usually a UNIX workstation running a rarpd daemon) performs this function using two configuration files and one or more daemons. The configuration files are “/etc/hosts” and “/etc/ethers” and the daemon is called rarpd. A name can be assigned to any device on a network and is arbitrary. For the following examples the name used for the OkiLAN 6200e is OKIPRINTER. Remember that this name is arbitrary; a customer can assign any name.
The “/etc/hosts” file is where each entry maps a host name to an IP address. An example entry is shown below.
The “/etc/ethers” file is where each entry maps a host name to a network hardware address. An example entry is shown below.
The following sequence of events occurs during the power up of the OkiLAN 6200e