Having some issues with Virtualbox internal networks? Maybe this will help.
Recently I had a right pain trying to get the internal network in Virtualbox working. Neither box would connect to it. I ended up adding a new one with a DHCP server attached. In theory you can just set the name in the command below to be inet to add a DHCP server to an existing network, but I chose to create a new one
$ vboxmanage dhcpserver add — netname testlab — ip 10.10.10.1 — netmask 255.255.255.0 — lowerip 10.10.10.2 — upperip 10.10.10.212 — enable
Inside the settings for the relevant virtual machines, set (or add a new network) of type internal and select testlab in the drop down list.
Your boxes should now be able to commune with one another.