VirtualBox/Networking

Internal Network

An internal network is a VM-to-VM network. Good if you have a Kali VBox and you're attacking a Metasploitable VBox, and you want to run it all on top of a Mac while you are, say, on a public wifi network and therefore don't want to expose either machine to the outside world.

Start by setting up internal networking on the virtual machine image: use a VM's "Settings" box in the GUI. Click "Networking", then pick "Internal Networking." This will use an internal network with the default name of "intnet".

Next, set up the DHCP server that will allow machines on the internal network to talk to each other and be assigned IP addresses. To do this, use the VBoxManager command line utility:

VBoxManage dhcpserver add \
--netname intnet \
--ip 10.2.0.1 \
--netmask 255.255.0.0 \
--lowerip 10.2.0.1 --upperip 10.2.0.255 \
--enable

If the DHCP server already exists, you can use the modify argument:

VBoxManage dhcpserver modify \
--netname intnet \
--ip 10.3.0.1 \
--netmask 255.255.0.0 \
--lowerip 10.3.0.1 --upperip 10.3.0.255 \
--enable

Finally, if you want to remove an existing DHCP server:

VBoxManage dhcpserver remove --netname intnet

Also see my answer here: https://superuser.com/a/1262469/322279