Network architects can use DHCP to automate the management of IP host configuration. The network architect's role is to configure the DHCP server with a description of the network architecture and rules for IP host configuration. The DHCP server then uses that configuration information to determine specific configuration parameters for each host. The network architect describes the architecture and host configuration rules to the server through a configuration mechanism, such as a configuration file or an interactive user interface.
The ISC DHCP server uses a configuration file that is read when the server first starts up. The network architect defines global and network-specific configuration parameters within the configuration file. As the ISC server receives DHCP messages, it consults the network description from the configuration file and determines the specific parameters to be passed to the IP host. This chapter introduces some of the most widely used features of the ISC server configuration file. Chapter 9 describes the DHCP options in more detail, and Chapter 15 elaborates on the format and use of the configuration file.