What I'm trying to do is create a host-only network with multiple VMs so as to allow direct access between the host OS and the VMs, but to also allow the VMs limited access to the Internet for things like software updates, NTP, etc.
FWIW, I can do this using an internal network ('intnet'). I have successfully set up a couple server appliance VMs (TurnKey Linux), a desktop OS VM (Debian), and a gateway/firewall VM (Smoothwall Express) that is dual-homed (one NIC on the internal network, and the other connected via NAT to the outside world). I set up the gateway machine as a DHCP server, the other VMs get their connection info from it, the server appliance VMs can connect for updates, and I can browse from the desktop OS VM to the Webmin control panels on the server appliances. Everything works as intended.
When I try doing the same thing on a host-only network so I can connect directly from the host OS (Ubuntu 11.10 Desktop) to the guest VMs... all sorts of weirdness ensues. Basically... it seems as though the host-only built-in DHCP server is over-riding any attempts to use any other DHCP server (like the one on the gateway/firewall VM), even when I turn it OFF in VirtualBox - even when I turn off the built-in DHCP server, turn off the program, restart it, and re-boot the guest VMs - they still either pick up their IP info from the built-in DHCP server (it doesn't change, despite the 'new' DHCP server using a different block of addresses), or aren't able to connect at all (can't get a DHCP lease).
I'm starting to wonder if I'm trying to do something that Virtualbox host-only networking just isn't capable of... Can anyone replicate this problem or point out what I'm doing wrong?