A bit of discussion about configuring VirtualBox guests using Host-only Adapter networking to access other guests on Host-only Adapter networks on other hosts.
In December 2013 a new version of VirtualBox, v4.3, was released, and among its few new features is a networking mode called "NAT Network."
The VMWare machine for Mac OS, Fusion, has released a new version, v4.
I've been a long-time user of Unbuntu, abandoning Windows on hardware some time ago. I swap between VMWare and VirtualBox to run Windows for occasions where I must, since I can do just about everything native on the Ubuntu desktop.
Wondering if this is a shortcoming on Microsoft's part, or something in the VirtualBox software.