Booting-Address Discovery

Summary of Address Discovery Protocols

When an NCD terminal powers up, it knows only its Ethernet or Token-Ring address, which is set in NVRAM at the factory. To participate on a network, a terminal must be able to discover its network address. Depending on your network setup, the terminal may need other information. The three ways for the terminal to discover addresses and other information before loading the X server are:

DHCP (Dynamic Host Configuration Protocol) and BOOTP (Bootstrap Protocol)-DHCP and BOOTP are widely available protocols, and are the recommended methods of address discovery. By default, an NCD terminal broadcasts alternating DHCP, BOOTP, and RARP requests when it boots. These requests contain the terminal's Ethernet or Token-Ring address. A host running the DHCP or BOOTP daemon and configured with information about the terminal responds with the IP address of the terminal.

Depending upon the protocol implementation and the information in the host's database, it can return other addresses and permit the terminal to boot from a host on a different subnet. It can also specify the X server that each terminal boots.

For more information about DHCP and BOOTP, see "Using BOOTP/DHCP for Address Discovery".
RARP (Reverse Address Resolution Protocol)-RARP is another widely available address discovery protocol. By default, an NCD terminal automatically broadcasts alternating DHCP, BOOTP, and RARP requests when it boots. These requests contain the terminal's Ethernet address or Token-Ring address. A host running the RARP daemon and configured with information about the terminal responds with the IP address of the terminal.

Unlike BOOTP/DHCP, RARP supplies only the address of the terminal and the address of the host that responded to the terminal's request for an X server. This method is recommended if you do not have BOOTP/DHCP on your network.

For more information about RARP, see "Using RARP for Address Discovery".
NVRAM-You can save all of the necessary network addresses in NVRAM, where they remain even when the terminal is powered off. This method is recommended if:

For more information about saving addresses in NVRAM, see "Storing Addresses in NVRAM" and Chapter 11, Boot Monitor and NVRAM.

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