Select the Macros tab.
All macros defined for this DHCP server are listed in the left pane.
Select the network macro whose name matches the network whose configuration you want to change.
The network macro name is the network IP address.
Choose Properties from the Edit menu.
The Macro Properties dialog box displays a table of the options included in the macro.
Select the option you want to modify.
The option name and value are displayed in text fields near the top of the dialog box.
Type the new value for the option and click Modify.
You can also add options here by clicking Select in the dialog box. See Modifying DHCP Macros for more general information about modifying macros.
Select Notify DHCP Server of Change and click OK.
The change is made to the dhcptab and the DHCP server is signaled to reread the dhcptab and put the changes into effect.