Per-folder VPN
If your servers cannot be reached from the internet, per-folder VPN is the way in. You configure it once on the folder and every server inside inherits it.
How it works
The VPN configuration is stored encrypted in the folder, just like a credential. When someone opens a session against a server in that folder, the tunnel comes up by itself; after fifteen minutes without use, it shuts down.
Each customer runs in their own isolated network space. Two companies using the same private range do not collide.
Inheritance
Same rule as credentials: a VPN set on a folder is used by every folder below it, and a folder that defines its own beats the inherited one.
From which plan
The Free plan only reaches servers available from the internet. Per-folder VPN starts at the Inicial plan.