Compaq T1500 manual Option 18 vs. Option 43 vs. Options 128+

Configuring Terminal Start-Up Resources 17

Option 18 vs. Option 43 vs. Options 128+

All three methods (Option 18, Option 43, Option 128+) provide identical capabilities, just in different manners. It is recommended that only one method be used, but you are not restricted to this. Things to take into consideration when choosing include the following: existence of a TFTP server, level of configurability in the DHCP server, availability of a binary file editor, knowledge of DHCP option data format, and the number of other devices that are going to be administered via DHCP.

Option 18

Option 18 is a standard DHCP option that provides the network address and pathame of a file to be obtained via TFTP. The standard format of this file (RFC-defined) is a set of DHCP options (option number, length, data), terminated with the end (255) option. Since in most cases this format is very difficult to edit, a text file format is also supported where the options are of the form LABEL=DATA, all entries are one per line, and all are ASCII data. Any option that can be passed as DHCP option data can be stored in the binary format; only those which are actually supported by the terminal are allowed in text format. All 128+ options as described above are also allowed in an option 18 file.

Table 2-3 lists the labels and data for the text format options.

Table 2-3 Labels and Data for Text Format Option

Option
Number	Label	Notes
1		Not allowed.
3	ROUTER	Put here with extreme caution.
4	TIMESERVER	Not currently used.
6		Not allowed.
9	LPRSERVER	Not currently used.
12	HOSTNAME	Put here with extreme caution.
15		Not allowed.
17		Not allowed.
18		Not allowed.
28		Not allowed.