VirtualBox Ubuntu guest: alternating between network adapters at home/office

Question

Edit: Added a use case for CIFS

Setup:

• Host: Windows 7 SP2 64bit
• Guest: Ubuntu 12.04.3 LTS 64bit (on VirtualBox 4.3.0)
• The host laptop has a 2 network adapters:
  • A USB-pluggable WiFi module
  • An 1Gbps ethernet port

Use cases:

• When working at the office, the USB WiFi module is connected to the host. The Ubuntu guest needs connectivity with a fixed IP configuration (A fixed IP on the 192.168.1.x network, DNS is 8.8.8.8)

• When working at home, the USB Wifi module is absent, and the Ethernet port on the host is used. The network at home has a DHCP server (my home router) which I want to use in order to assign IP configuration for the Ubuntu guest.

• In both cases, I want the Ubuntu guest to work in "Bridged" mode (bridge the virtual eth0 and/or eth1 to the host's currently-used physical network adapter).

• I need the host the guest to communicate over CIFS (samba) which I think prevents me from using NAT (?)

• Unfortunately, I noticed that when the USB WiFi is disconnected from the host, VirtualBox automatically switches the physical device used for "virtual network interface 1" to the Ethernet port.

My question:

When working either at home or at the office (that is: either with the USB WiFi connected and the Ethernet disconnected, or the other way around), I want to have Internet connectivity on the VirtualBox, without the need to manually change the configuration every time.

• What configuration should I use in VirtualBox?

• What configuration should I use in the guest? Specifically, in /etc/network/interfaces, in /etc/udev/rules.d/70-persistent-net.conf

• Also, does the guest need any specific IP routing rules so that traffic is routed through the (always single) available guest interface?

• Does a specific configuration of bridging host interfaces (Use Windows to bridge the Wifi and Ethernet adapters) help in any way? What are the VirtualBox and guest configurations in this case?

Answer 1

NAT allows incoming connections when configuring port forwarding but as far as I know, this won't work with CIFS at least if you want a CIFS servers on the guest side.

If you just want your guest to be a CIFS client and the server to be on the host, NAT might just work.

In any case, what I would do is configuring two interfaces on the guest.

• The first one would use NAT so allow Internet connection.

• The second one would use a "Host Only" network, i.e. vboxnet, and will allow unrestricted bidirectional communication between the host and the guest.