How to do multiple scenes/servers in Unet ?

I was just wondering if anyone knows what the standard idea behind how to do this is using Unet?

Is multiple scenes even possible with a single server?
If not, how would you connect multiple servers hosting different scenes together ?

Would you have players disconnect from one server and connect to another while they are "zoning" between areas or something like that?

I was just wondering how is this typically done in online gaming, and what the Unet solution is theoretically supposed to be?