Both servers, main and backup, must be listed on the Servers tab of Domain options.

1.To open the Domain's configuration window, click the E3 Admin icon on Windows Notification Area and select the Domain - Options menu.

Domain - Options menu

2.Servers may have any name in the Server name field. In the Network address field, type the computer's name on the network. For example, Server name as "Server1" and Network address as "\\Server1".

Servers tab