What we have done to solve this problem is to create two network adapters on the guest virtual machines. One for the public connection to the outside world and one for the internal connection from host <-> guest.
Keep your first interface the same as it is now.
Create a second interface with the type: Host Only.
Important NOTE: If you have never created a host only adapter, you must do this before you create the Host only interface in the guest. Go to File -> Preferences -> Network, then add a host only network. You may want to confirm that DHCP is enabled on this interface at the same. This will create the interface on the host system so it can communicate with the guest systems.
Boot up the guests and you should see two interfaces. The first interface, probably eth0 in your setup, should be your bridged network adapter. The second interface, probably eth1, should be your host only adapter. In my setup this is a 192.168.x.x address. On the host OS, a new interface was created called vboxnet0 this should also have a 192.168.x.x network. All of these together will give you the ability to talk with each other internally.
