My host machine is in a 192.168.2.0/24 subnet and I wanted to set up a 10.0.0.0/8 network with various hosts in VirtualBox that talk to each other. So VirtualBox should act as a router between those two networks. Now in VB I have the choice between bridged network which wouldn't work and NAT which I don't want, since I just want to have a normal subnet without NAT.
How could I achieve this? Is it possible?
VirtualBox alone will not function as a router. You will need an additional application on a virtualized instance to handle that. Any of the firewall OS packages or any OS that can be configured to route can be virtualized within VirtualBox to accomplish the routing - Vyatta and Smoothwall are some of the common OS packages. Just enable two NICs for that VM, one bridged and another for Internal Network. The other VMs can then also be placed on the Internal Network.