In DWG workmode:

• When attaching a reference, you can specify a level for the reference attachment.

  In an AutoCAD DWG or DXF file, each XREF or layout viewport is placed on a specific layer. When you open the DWG file in Bentley Raceway and Cable Management, XREFs and layout viewports are treated as references, and are placed on the same levels (layers). To modify a reference's level, open the References dialog, double-click on the reference to open the Attachment Properties dialog, and modify the Level setting.

  If a level is frozen, references on that level are not displayed.

• A model cannot be attached to itself as a reference (self-reference).
• Clipping masks cannot be used on references.
• You can work with live nested references, but cannot turn off live nesting or control nesting depth, except by using the Ignore Attachment when Live Nesting setting (Attachment Properties dialog.)