Select the Xconfig file in which you want to configure XDMCP startup modes and open the Xconfig dialog box. You can configure the following settings for XDMCP Query, Broadcast, and Indirect startup modes in the Miscellaneous area:
Display Class Groups classes of XDM nodes. The Display Class box is applicable only when XDM-AUTHENTICATION-1 or XDM-AUTHORIZATION-1 is enabled on the XDM host. Do not modify any of these values unless requested by your system administrator.
Enable XDM Authentication Enables XDM Authentication.
XDM Authentication Key Defines the display key used in XDM authentication. The authentication key is applicable only when AUTHENTICATION-1/AUTHORIZATION-1 is enabled on the XDM host. If it is enabled, your system administrator requires your Display Class and XDM Authentication Key. Do not modify any of these values unless requested by your system administrator.
Starting in XDMCP Query Startup Mode