Export To LandXML dialog box
Opens via: LANDXMLEXPORT command
The Export To LandXML dialog box allows you to select which entities you want to export by their type or by selecting them in the drawing.

Select all
When checked, all entities in the drawing are selected for export.
Select objects in drawing
Click the select icon () to temporarily dismiss the Export To LandXML dialog box and select entities in the drawing to export.
Export
Opens the Save LandXML file dialog box where you can specify the location and name of the output LandXML file.