Information on BOOTP Vendor Extensions and DHCP Options

The Bootstrap Protocol (BOOTP) describes an IP/UDP bootstrap protocol (BOOTP) which allows a diskless client machine to discover its own IP address, the address of a server host, and the name of a file to be loaded into memory and executed. The Dynamic Host Configuration Protocol (DHCP) provides a framework for the automatic configuration of IP hosts. See how to install DHCP on Windows Server 2019, perform Post-deployment of DHCP Server, how to configure DHCP Server option 60, 66, and 67 for WDS, and For more information on Automatic IP Assignment: Dynamic Host Configuration Protocol (DHCP).

DHCP options provide specific configuration and service information to DHCP clients. These options appear as variable-length fields at the end of the DHCP messages that DHCP servers and clients exchange.

An option space is a collection of options. ISC (Internet Systems Consortium) DHCP has five predefined option spaces: dhcp, agent, server, nwip, and fqdn. The NIOS appliance supports only the predefined DHCP option space, which contains the industry standard options as well as additional options you can configure as needed.

• Predefined options: These are option codes 1 to 125. They are allocated by the IANA and defined by IETF standards. The DHCP server knows these standard options, and they are predefined on the server. You cannot redefine these options or delete them from the DHCP option space.
• Custom options: These are option codes 126 to 254. They are not defined by IETF standards and are available for private use. You can use these option codes to provide configuration or service information that none of the predefined options provide.

You can also create option spaces to define new groups of options. For example, you can create additional option spaces to define vendor-specific options encapsulated in option 43. When a DHCP client requests vendor-specific options, it makes a request using the vendor identifier set in option 60 and a list of requested vendor-specific options (option 43). The DHCP server then responds with the list of replies for the various options encapsulated in option 43.

Note: Custom options defined in the DHCP option space are included in the options section of the DHCP messages that DHCP servers and clients exchange. Custom options defined in a user-defined option space are always encapsulated in option 43 in DHCP messages.

See the below table for BOOTP Vendor Extensions and DHCP Options

I hope you found this blog post helpful. If you have any questions, please let me know in the comment session.