HP-UX LAN Administrator's Guide (Feburary 2007)

DRAFT COPY LAN Device and Interface Terminology
RARP Configuration
Chapter 8 143
RARP Configuration
RARP (Reverse Address Resolution Protocol, RFC 903) configuration is an optional
addressing scheme in which a freshly booted system queries a network server for the IP
address of its own networking interface.
For example, if you have a large installation with many nodes, you can centralize the IP
address database onto a system that serves as a RARP server. When each client system wants
to configure its network interface, it queries the RARP server to provide the information listed
in its database. In this way, each client system does not need to have its own customized
version of the netconf file to contain its IP address.
When an interface needs to be configured with an IP address specified by a RARP server, the
/usr/sbin/rarpc program is used to broadcast a RARP request over the network connected
to the interface for which the information is being requested. If there is a RARP server on that
network, and if the hardware address for the client interface is in the server’s database, then
the server will send a response to the client containing the IP address of that interface. The IP
address is then passed to the configuration script, which uses it to configure the interface.
Setting Up a RARP Client
An interface is configured to use RARP configuration when the IP_ADDRESS variable in the
/etc/rc.config.d/netconf file is assigned the value of RARP. The IP address variable is an
array, each element of which corresponds to a particular interface number. Usually, this
variable contains an explicit IP address, which is used to configure the interface specified by
the INTERFACE_NAME variable.
To configure an interface to use RARP, the /etc/rc.config.d/netconf file must be modified
so the IP_ADDRESS variable is set to RARP. This can be done with a text editor such as vi, and
it can be done for interface entries other than 0. For example, for interface entry 1 to use
RARP, the IP_ADDRESS line should be modified to IP_ADDRESS[1]=RARP. If the interface name
for entry 1 is specified as INTERFACE_NAME[1]=lan1, then interface lan1 will be configured
with RARP information when the system is next booted.
When making this modification, the IP address should be recorded so the appropriate entry
can be added to the server database.
Setting Up a RARP Server
A system is set up to be a RARP server when the RARPD variable in
/etc/rc.config.d/netconf is set to 1. Usually, this variable is set to 0 so that a RARP
server is not started.