and making sure the VM is not set up as bridged networking, I personally have a pfSense VM and route my computer and all my other VMs to it each on a separate virtual NIC with firewall rules etc.
look at my profile for a link to my blog where I explain things in detail, it's not finished (I still have to write a post about how I configure i3 and how I start virtualbox more easily) but the pfSense stuff should be ready for public consumption
