Option 48 assumes TCP and port 7100 for font server access. If other ports are to be used, you must use the vendor-specific option described below. Also, option 49 assumes Query mode. If Direct is wanted, use the vendor-specific option.
The terminal uses options 66 and 67 to determine where to obtain the operating system for the network-booted terminal, with option 66 being the server name (as an IP address), and option 67 being the full pathname to the file (such as /tftpboot/vmlinux). Option 17 is the IP address and path name to the root directory (similar to the T17 entry for BOOTP) and is of the form IPADDR:/pathname.
Option 18 (extensions path) operates as follows: If the extensions path option is given, it is treated as a <machine>+<directory-path>pair, with a colon separating the two. Directory separators are UNIX separators. Typically, this would be of the form: 132.237.20.164:/tftpboot/extension.opt, where the suffix is anything but .txt to behave consistent with RFC 2132. If the suffix is
.txt (case is ignored), the file is treated as a text list of options in the form option=value.
Although this violates the RFC, text files are much easier to manipulate using an editor than is a DHCP option space. The IP address and pathname used above are only for example. Table 2-2 lists all T1500-specific options not listed in Table 2-1. Note that binary options can not be passed (as binary) in the text mode associated with this option.
If the DHCP server is capable of returning values for option 43 based upon either vendor or client ID (or some other tag), the current software release will utilize this data. The format of this option is an encapsulated format, consistent with RFC 2132. Identical options are available here, through the extensions path and through options 128+ (discussed below), although option 43 predefines the "option" numbers, while the others do not (unless option 43 is passed in the extensions path file).
Additional vendor-specific options are available to disable swapping and to provide a network services directory. These options are listed in Table 2-2 and sit in option space 128-254. Setup provides the ability to modify the set of options sent by the terminal to the server at DHCP negotiation time. By default, none of options
128-254 are requested. All vendor-specific options in the 128-254 option space are strings of the form 0080_TAG=DATA, where TAG and DATA are illustrated in Table 2-2. It is recommended that, where possible, options 43 and 18 be used rather than the 128-254 option space.