How to create isolated VMs in Oracle VM VirtualBox?

[Nikhil Tamhankar]

I want to create two completely isolated VMs (Ubuntu) using Oracle VM VirtualBox on my work PC but I want those VMs not to connect to my work network. I want only those two VMs to communicate with each other but NOT with Host (Windows 7) or any other computer in company network.

I want to do this because I just want to practice Linux commands.

Bottom line, I need two VMs (Ubuntu) on Host PC (Windows 7) which should neither communicate with host or any other computer in company network. Those two VMs should only communicate with each other.

Can anybody help to push me in the right direction to create such types VMs?
Additional Details
I know there are 8 network types in VirtualBox and which one should I go with:

Introduction to networking modes
Each of the eight networking adapters can be separately configured to operate in one of the following modes:

1) Not attached
2) Network Address Translation (NAT)
3) NAT Network
4) Bridged networking
5) Internal networking
6) Host-only networking
7) Generic networking
7.1) UDP Tunnel
7.2) VDE (Virtual Distributed Ethernet) networking

Which one is best suitable for me as per the scenario I discussed?

[Martin]

If your read through the manual Chapter 6. Virtual networking you will find that "internal networking" is what you are looking for.

[Nikhil Tamhankar]

Thank you very much. It really helped.