Option 43 is a
binary buffer, containing a list of sub-options.
Sub-options are packed in the binary buffer in no specific order.
Most sub-options are optional.
An exhaustive
list of sub-options can be found in the
PXE specifications. Only sub-options of interest to specify the IP
address of the PXE server are described here. Other configurations,
like multicast discovery, multiple unicast servers, or multiple choices,
are not explained in this section.
- PXE option 6: PXE_DISCOVERY_CONTROL
- This option
specifies how the PXE client contacts PXE servers,
using either unicast, multicast or broadcast. The format of this option
is one byte.
- PXE option 8: PXE_BOOT_SERVERS
- A list of IP addresses, each address corresponding to one PXE
server (when discovery_control is unicast). A PXE server
is identified by a number (the standard value for Tivoli® Provisioning Manager for OS Deployment is
15) and its IP address. The format of this option is two bytes for
the server type (15 for Tivoli Provisioning Manager for OS Deployment),
one byte for the number of servers to list (1 in our example), and
four bytes per server address.
- PXE
option 9: PXE_BOOT_MENU
- This option contains a list of
choices to prompt on the screen
at boot time. You need to have a PXE boot menu even if it is not
used. The format of this option is two bytes for the server type,
one byte for the length of the string to display, and the string
to display on screen. The total length of this option is be 5 bytes.
- PXE option 10 (0A): PXE_BOOT_TIMEOUT
- This option is required to specify how long (in seconds) the boot
menu is displayed, and the text of a prompt that is displayed during
waiting time. The format of this option is one byte for the timeout
value, followed by the prompt text.
- PXE
option 255 (FF): PXE_END
- To be valid, the binary buffer
of DHCP option 43 must end with FF.