I'm using docker with elubow/cassandra and can start 3 machines.
I have a virtualbox ubuntu guest with cassandra installed and I want it to be the base node. The three docker machines should be seeds to the vbox instance. 

Without using bridged networking (giving IPs on the physical network) I want to have the ubuntu guest see the other cassandra nodes, and using port forwards, allow my host machine to connect to certain ports on ubuntu. 

I can create the NAT network in vbox, and can create a similar one with docker network create, but its not the same network, and docker doesnt seem to know about the one created in vbox or vice-versa. How can I make all these guests use the same NAT network?