digitalocean - docker-machine uses public IP instead of private IP

Hi, I defined digitalocean-private-networking=true in the MachineOptions and the docker-machine uses the same VPC. Therefore I expected, that all communications between the docker-machine and uses the private IP addresses.

But docker-machine ip shows the external IP address and if I add the docker-daemon port to my firewall only for the VPC, then the machine will be started via the digitalocean API... but the CI Job hangs.

I found some other users who expected that only the VPC will be used.

Another strange thing I noticed by inspecting the logs on the bastion host is that it seems the communication between bastion and runners is not happening on the private network despite the setting that says the contrary. I may be wrong though, as I’m new to DO networking.

Quote: https://www.digitalocean.com/community/tutorials/how-to-autoscale-gitlab-continuous-deployment-with-gitlab-runner-on-digitalocean?comment=76982

.. and another one: https://www.digitalocean.com/community/questions/how-to-force-docker-machine-to-use-private-ip-instead-public

Is there a possibility to force that the communication uses only the private IP adresses?