draw dotted/dashed rectangles in Eagle schematic
Symbol, net, info, etc. are different layers within the editor. Changing the layer of a line may or may not change its color, but has no other effect on its style or width.

You need to use the "change style" command. You can select Continuous, LongDash, ShortDash or DashDot.

Also, when you're laying down wires, there's a "Style" dropdown available on the toolbar.