Virtual ip range

Hi all

I am running proxmox 3.1 currently with my internal ranger 192.168.1.x which works great with my vm's

I want to make some training videos but want the new servers I create to have say a 172.160.0.x range but still be able to have outbound internet access to update the machines etc. I only have 1 nic installed but happy to fit another 1 if need be

What is the best way to go about this please

Thanks

Glenn