A viewport is added to a layout tab while in paper space and allows you to view the objects in the model tab. Having a viewport in a layout is what allows you to switch between model space and paper space. If there are no viewports in the layout and you try switching to model space, you’ll receive an error in the command line saying, “There are no active Model space Viewports.”
When you switch to model space, while in a layout tab, you can use any command to add or modify objects in the model tab. This allows you to position the objects, using the standard view and navigation commands, and then dimension or annotate anything in the model tab.
The default layouts, in the standard Toolbox drawing template, all have one viewport already placed in paper space. You can see this viewport as a turquoise box in paper space. This entity is placed on its layer called “VPORT.” It is always recommended to keep all viewports on their own layer, so this layer can be turned off before you print. When you add your viewports to a drawing, they won’t be automatically added to this layer, so each viewport entity should be changed to the “VPORT” layer to identify it better.
You can place as many viewports in a layout as needed. Having multiple viewports allows you to set up a printed sheet of paper with multiple views. When placing new viewports, it is a good practice to remove all existing viewports in paper space. This will prevent two viewports from being placed on top of each other and causing viewing errors. When you are ready to place viewports in paper space, you can use the One Viewport, Two Viewports, Setup Viewports, or PaperSpace Viewports commands from the Navigate drop-down to setup the viewports. When you have multiple viewports in paper space and switch to model space in a layout tab, you will first need to pick a point in the viewport for it to become active. Once a viewport is active, you will see its border become highlighted, and commands entered into the command line will now affect that viewport.