Level 4
This is a good recommendation and makes sense.
Quote: The reasoning behind it is simple. By keeping all the IoT equipment on a separate network, any compromise of a "smart" device will not grant an attacker a direct route to a user's primary devices -- where most of their data is stored. Jumping across the two networks would require considerable effort from the attacker.
In other words don't make it easy for the cyber criminals to do any damage.