Using Ubuntu 8.10 amd64, updated from RC
I was able to setup VirtualBox Host Networking with this tutorial here:
However, after using the system for a few days, I noticed instances where the system would lose all connectivity and would not regain it until a reboot. Trying various solutions previously stated within this bug report provided no satisfactory solution. As a work-around I uninstalled network-manager using aptitude, then manually configured all interfaces in /etc/network/interfaces:
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
iface lo inet loopback
# The primary network interface
iface eth0 inet static
#VirtualBox interface bridging for Host Networking
iface br0 inet static
bridge_ports eth0 vbox0 vbox1 vbox2
Use the values appropriate for your own situation, but do mind the configuration of br0, as it overrides the configuration of eth0. Myself I'm using static IP addresses; to use DHCP just set both to use dhcp. Afterwards changed /etc/NetworkManager/nm-system-settings.conf so the ifupdown plugin is set to false (I had previously set it to "true"):
Then manually edited /etc/resolv.conf with the settings I wanted:
This lets me use the 2wire DSL functions and OpenDNS's nameservers, as my ISP's nameservers fail constantly.
Rebooted system, networking works as expected for both the Host and Guest systems. I do realize this is not the most appropriate place to post this information, but I thought it important to have a written workaround somewhere. As usual, your mileage may vary depending on your own system setup.