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Using BOOTP/DHCP for Address Discovery

This section describes preparations for using BOOTP/DHCP. For BOOTP, you can use the native software on the boot host or the software included in the NCDware distribution.

If you are using DHCP to provide network information, the terminal configuration is the same as for BOOTP, and the terminal must have Boot Monitor version 2.8 or later.

If you are not using ncdinstall to prepare hosts and terminals for BOOTP/DHCP service, you need to perform the tasks described in the following subsections. The commands and steps may vary from those outlined in this section depending on your host, your BOOTP/DHCP implementation, and your network. These instructions are guidelines; they are not precise procedures.

NCD terminals send BOOTP/DHCP requests by default; consequently, terminal configuration is unnecessary unless you want to change the order in which the terminal sends requests for network information or specify a second or third source. The default order is first DHCP, then BOOTP, then RARP.

Information provided by BOOTP (for example, the subnet mask) is passed to the X server and may be stored in NVRAM, overwriting previous values.

The BOOTP protocol is implemented through daemon programs, such as bootpd(8), and a database file, such as /etc/bootptab. Hosts configured to use NCD's dynamic IP address allocation for terminals use an additional database file, /etc/bootptab.cfg.

For specific instructions on using BOOTP, refer to the following sources:

For Information About:
Refer to:
NCD's BOOTP implementation The bootpd man page in the NCDware distribution
The native BOOTP already installed on your host Your host's documentation
BOOTP/DHCP options recognized by NCD terminals Table 3-1
Dynamic IP address allocation using BOOTP The bootpd (8) and bootptab.cfg (5) man pages in the NCDware distribution and the System Administrator's Guide.

For instructions on using DHCP, refer to your host system's documentation.

Making Sure that BOOTP Is Enabled

To verify that BOOTP is enabled on your boot host, check the following:

Adding Options for NCD Terminals to the bootptab File

If you do not use ncdinstall to add terminals to the network, you must add BOOTP options for each terminal to the /etc/bootptab database file on the boot host.

bootptab Format and Options

For BOOTP configuration on your boot host, see your vendor documentation. The normal rules for /etc/bootptab file entries are:

The typical file structure is one or more template entries, containing information common to all terminals or a group of terminals, followed by individual entries, each containing information about a specific terminal:

# Template entry
# Entry for an NCD terminal

The tags recognized by NCD terminals and supported by the version of bootpd provided in the NCDware distribution are listed in Table 3-1. The table lists the normal two-letter tag name or a tag number and a description of the information provided by the tag. Although some versions of bootpd may provide additional information, only information listed in the table is used by NCD terminals.

Table 3-1 BOOTP/DHCP Tags Used by NCD Terminals
Tag Name
Information Returned by BOOTP or DHCP
ip Terminal IP address
ha Terminal Ethernet address
hd X server directory
bf X server filename
sm Subnet mask
gw Gateway address(es)
ns IEN-116 name server host address(es)
ds Domain name server host address(es)
cs Vendor magic-cookie selector
hn Terminal host name (you do not need to supply a value for this field; it is taken automatically from the first field [up to the first colon]).
ts Names of hosts supplying the current time on UDP port 37
T15 Domain name suffix
T144 Configuration file name
to Time offset from Coordinated Universal Time
ts Time server host address(es)
T31 ICMP router discovery enabled
T28 IP broadcast address
T49 XDM (X Display Manager) host address(es), listed in order of preference

A fragment of an example bootptab file follows, with comments identifying the fields.

# Template entry
global:\ Template entry name
gw=\ Gateway address
sm=\ Subnet mask
hd=/tftpboot:\ X server file directory
ht=ether Interface name
# Entry for an individual NCD terminal
ncd1:\ NCD terminal's hostname
tc=global:\ Include the template
ha=0000a70015d5:\ Ethernet address
ip=\ IP address
bf=Xncdxpl X server filename

Adding Terminal Entries to the bootptab File

The required and optional entries in the bootptab file are:

Configuring the Gateway Device and Terminal for Booting through a Gateway

For booting through a gateway, the device serving as the gateway and the bootptab file on the boot host must be properly configured.

This section provides an example setup (illustrated in Figure 3-1) for a Cisco router, which is a commonly used gateway device.

The IP addresses of the gateway's Ethernet interfaces are: Ethernet Interface 0-for the remote network where the boot host is located. Ethernet Interface 1-for the local network where the terminals are located.

The IP address of the boot host is

The IP address of the NCD terminal is Its Ethernet address is 0000a70023a3.

On the router, set the helper address to the address of the remote boot host by entering the following command:

ip helper-address

On the boot host, the bootptab file contains the following entries for this example:

# Template entry - every host uses this information
:sm=\ Subnet mask
:hd=/tftpboot/Xncd.4.2.0: X server file directory
# Entries for each subnet
subnet.one:\ Include the template and specify the gateway address
subnet.two:\ Include the template and specify the gateway address
# Entry for an NCD terminal
ncdhmx1: tc=subnet.two:\ Include the template
:ht=ethernet:\ Network interface type
:ha=0000a70023a3:\ Terminal Ethernet address
:ip=\ Terminal IP address
:bf=Xncdhmx X server filename

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