option dhcp-parameter-request-list uint16;

This option, when sent by the client, specifies which options the client wishes the server to return. Normally, in the ISC DHCP client, this is done using the request statement. If this option is not specified by the client, the DHCP server will normally return every option that is valid in scope and that fits into the reply. When this option is specified on the server, the server returns the specified options. This can be used to force a client to take options that it has not requested, and it can also be used to tailor the response of the DHCP server for clients that may need a more limited set of options than those the server would normally return.