AutoCAD LT does not allow circular references between external references. A circular reference occurs when you use as an xref a drawing that contains an xref to the current drawing. If AutoCAD LT detects this problem when you are attaching an xref, it terminates the command and undoes its effects up to that point.
If AutoCAD LT encounters a circular reference while loading a drawing, it displays an error message and displays a single piece of text for each instance of the xref.
If AutoCAD LT detects a circular reference when reloading an xref, it displays a warning, ends the command, and undoes the effects of the reloading up to that point.