A TCP/IP host uses the DHCP (Dynamic Host Configuration Protocol) to obtain its configuration parameters (IP address, gateway, name servers, and so on) from a DHCP server that contains the configuration parameters of all the hosts on the network.
The QNX Neutrino DHCP client, dhclient, obtains these parameters and configures your host for you to use the Internet or local network.
If your DHCP server supplies options (configuration parameters) that dhclient doesn't know how to apply, dhclient passes them to a script that it executes. You can use this script to apply any options you want to use outside of those that dhclient sets for you. For more information, see the entry for dhclient in the Utilities Reference.