Jumpstart Network Boot Protocol - RARP

        Normally, The install server provides the boot program for booting
        clients. However, under one condition, the Solaris network booting
        architecture requires you to set up a separate "boot server". A boot
        server is a system with just enough information to boot up a client
        over a network. You have to setup a boot server when the install
        client is on a different subnet than the install server.
       
        SPARC install clients require a boot server when they exist on
        different subnets because the network booting architecture uses the
        reverse address resolution protocol (RARP). When a client boots, it
        issues a RARP request in order to obtain its IP address. RARP, however
        does not acquire the netmask number, which is required to distribute
        information across a router on a network. If the install/boot server
        exists across a router the boot will fail because the network traffic
        cannot be routed correctly without a netmask number.
       
        The result is that you can install a client across a router, but you
        cannot boot a client across a router. So you will have to setup a
        separate boot server on the same subnet as the client.