The Default Facility must be allowed to login, otherwise you’ll generate an error when accessing the User_Login.aspx page, with ERR_TOO_MANY_REDIRECTS. This is caused by the system trying to determine what interface to use to log users in. This also can happen if there are no user interfaces configured for the Default Facility.

Note that if there is no Facility that is explicitly defined as Default, then the first Facility entered in to the system (usually with an ID of 1000) is generally accepted as the Default.