This page describes the process of loading the ViewStation's IP address
with RARP, the Reverse Address Resolution Protocol.
IP
Addressing with RARP
The RARP (Reverse Address Resolution
Protocol) is another mechanism to set the IP address. RARP doesn't have
the capability to specify a boot file. (If you want to use the
download option, you should use the BOOTP daemon for both IP address
resolution and the boot file location. If you just want to download the
server code, you can use the Startup Options menu directly without
using BOOTP at all.)
The RARP (Reverse Address Resolution Protocol) daemon needs
two files, one to match the hardware address to a name and another to
match the name to an assigned IP address. (In the example below, these
files are named /etc/ethers and /etc/hosts respectively. These file
names may be different on your system.)
When you turn the ViewStation on, it sends a broadcast message
containing its hardware address out on the network. The RARP daemon
receives this message, checks the /etc/ethers file to match that
hardware address to a name, then checks that name in the /etc/hosts
file to get the IP address to return to the broadcast source. Correct
operation of the RARP protocol obviously requires that the information
for the ViewStation be entered correctly, particularly that the names
used are identical (most systems don't have a rigid syntax for the
names, but whatever is used must be used consistently). Changes to
these files are registered only when the RARP daemon starts, so you
will have to shut it down and restart it whenever you change the files.
Sun NIS IP Addressing
Recent versions of the SUN
operating system use NIS, Network Information Service (formerly called
SUN Yellow Pages), instead of RARP. Refer to the SUN documentation for
details on NIS operation, but note that the /etc/ethers and /etc/hosts
files are replaced by NIS maps. These maps can be created automatically
from the RARP files with SUN conversion routines, usually found in
/var/yp.
RARP Protocol Example
This example deals
with one particular system of network operation. Each system is
different, with different host configurations, network arrangements, and
operating system variables. Check your system carefully to see what
its names, configurations, and requirements are. Use the man command
to look at your online documentation to see what the arguments for the
commands are and the syntax for the required files. Refer also to the
section of your documents called "Networking Services", or something
like that, for additional information.
The RARP protocol requires two files, one to match the
hardware address to a name, called /etc/ethers, and one to match the
name with an IP address, called /etc/ hosts. These two files are shown
below:
The ethernet file is /etc/ethers. Its form is as follows:[Ethernet hardware address] white space [host name]
00:80:96:00:44:a5
hds12
The hosts file is /etc/hosts. Its form is as
follows:[IP address] white space [host name]
128.91.4.12
hds12
The host name, for this example, has no definite
syntax, but must be identical to the entry in the /etc/ethers file.
The syntax and punctuation of the addresses may also vary from system to
system.
The RARP daemon must also be configured in a similar way, with
files such as a rarp.rc and/or an rarp.ifconfig. The RARP daemon, in
this example, is found in /usr/etc/rarpd. These names and locations
depend on your system. Changes to these files are only registered
when the daemon starts, so you will have to kill the daemon and restart
it whenever you make changes.
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