External Reference Palette - Xref

You can use External Reference palette to Attach, Unload, Reload, Detach reference files
View tab > Palettes panel > External References palette

 

When a drawing attached an external reference

 

A Manage Xrefs icon appear on the right-corner of the Status bar
Click the icon to open the External Reference palette

If an Xref file cannot be found

 

A warning box open to enable you to relocate the reference file

Use of External Reference

Change to Tree View to show the relationship between host and reference drawings

In the bottom pane, you can select the Detail view or Preview