Many people have questions about the different ways to connect to OCI. Having in mind how open is the Internet you would probably want to secure the communications between your on-prem environments and the cloud.
A simple way of doing it is using VPN software. Libreswan is a great alternative when you are looking for something reliable and open source.
The following diagram shows the architecture used in the whitepaper. The idea is to connect your on-prem networks with the applications running in the Virtual Cloud Network (VCN) in a private and secure manner.
You can find a step by step guide (33 pages) here: