The dhcptab File

The dhcptab file contains all the information that clients can obtain from the DHCP server. The DHCP server scans the file each time it starts.

The DHCP protocol defines a number of standard items of information that can be passed to clients. These items are referred to as parameters, symbols, or options. Options are defined in the DHCP protocol by numeric codes and text labels, but without values. For example, some commonly used standard options are shown in the following table.

Table 8-1 Sample DHCP Standard Options

Code	Label	Description
1	Subnet	Subnet mask IP address
3	Router	IP address for router
6	DNSserv	IP address for DNS server
12	Hostname	Text string for client hostname
15	DNSdmain	DNS domain name

Some options are automatically assigned values when the administrator provides information during server configuration. The administrator can also explicitly assign values to other options at a later time. Options and their values are passed to the client to provide configuration information. For example, the option/value pair, DNSdmain=Georgia.Peach.COM, sets the client's DNS domain name to Georgia.Peach.COM.

Options can be grouped with other options in containers known as macros, which makes it easier to pass information to a client. Some macros are created automatically during server configuration, and contain options that were assigned values during configuration. Macros can also contain other macros.

The format of the dhcptab file is described in dhcptab(4). In DHCP Manager, all the information shown in the Options and Macros tabs comes from the dhcptab file. See "About Options" for more information about options, and "About Macros" for more information about macros.

Note that the dhcptab file is a text file, but should not be edited manually. You should use either dhtadm or DHCP Manager to create, delete, or modify options and macros.