I'm trying to set up a virtual LAMP server, including sharing files between the guest OS (Ubuntu Server) and the host OS (Windows 7) using samba. I think my problem is that I can't get Bridged (or Host-Only) networking to work in VirtualBox.

I can boot the Linux VM just fine with NAT, but then can't access any services on it directly (except after port-forwarding port 80)(my understanding is that port-forwarding works because I'm not running a web server on the host OS, and therefore it can forward traffic to the unused port 80).

I don't think that port-forwarding samba traffic (from the host to the guest) will work since I think that the host OS is using those ports.

When I turn off NAT and turn bridged networking on I get an error. The VM fails to boot, with a dialog popping up (title: VirtualBox - Error) that says "Failed to open a session for the virtual machine UbuntuServer. Configuration error: Failed to get MAC address (VERR_CFGM_VALUE_NOT_FOUND).

I'm hoping that once this is resolved then samba will work ok :)

Any advice on this would be great (how to fix it would be wonderful, next steps for troubleshooting would be great, too :) )

4 Answers 4


So it looks like I happened upon an answer. I was fiddling around with the VM manager program (on the host OS) and made the 'Bridged' adapter #1 and now things work fine. Host-only also works once it's #1, too.

(I started with the default: NAT as adapter #1, then added the Bridged adapter as #2. Once I realized that the bridged/host-only adapter wasn't working I disabled adapter #1 (the NAT) leaving the Bridged adapter as #2)

  • BTW - I know that answering my own question is a bit gauche - if anyone can offer a clear explanation about why this is happening (or improve on my answer is some other, substantial way) I'd be happy to mark that as the answer, instead. Nov 25, 2012 at 21:04
  • Make sure which ever adapter you have set to 'bridged' is briged to your Microsoft Loopback adapter, and the adapter you want to access the internet is attached to NAT. This is done on the host through the VM manager. Then on your Ubuntu host, adapter 1 will be 'eth0' and adapter 2 will be 'eth1'; so if 'adapter 1' is bridged then 'eth 0' will be the static 192.168.x.x IP and 'eth 1' will have to be set to DHCP ... does that make since or am I totally misunderstanding the overall issue?
    – txtechhelp
    Dec 4, 2012 at 5:34
  • Also, which version of VBox are you using? They've updated a lot of their networking stacks and other internal features over the past few iterations.....
    – txtechhelp
    Dec 4, 2012 at 5:35
  • 2
    Answering your own question is considered fair practice here.
    – uSlackr
    Jul 6, 2015 at 13:47
  • My bridged adapter is #1 and it still stops working after some hours of working fine.
    – domih
    Jun 7, 2017 at 9:09

I solved it different than these answers. Using VirtualBox 4.3.10 , I simply had to do the following:

  1. Setup my VMs to use DHCP or Manual IP.
  2. IN VBox settings, if Nat networks has no value, add a NAT network with default settings.
  3. In VBox settings, if Host-only Networks is empty , add one called Host-Only Ethernet Adapter #2 ( I assume #1 would also work)
  4. Restart your VM. It will get the IP and it will now be able to access the internet using Bridged networking per VM instance.

Pretty wierd and obscure that this didn't work out-of-the-box.


It seems there is a problem with the many VBoxNetDHCP processes which are reduced by number but some are remaining in the host servers process list when VirtualBox is being closed. Kind of zombie processes.
I have a VirtualBox Host Server at Win7 and two guests with Win7. After a week the machines were not reachable over the network. I have configured 2 interfaces:

  1. Network bridge
  2. NAT Network

My fix at this time was to shut down all guest VMs, close VirtualBox management console and kill one VBoxNetDHCP on the host server (the others quit then by themselves). Then I started the VirtualBox and the VMs again and internet was back.

Previously a reboot of the whole hostserver worked too, but that is an even worse solution.


The bridged network mode in Virtualbox should work fine, it appears that your VM hasn't been assigned a MAC address (which should be different from your that of your physical NIC)

Attached is an image of the network settings for a VM in bridged mode, in the advanced section be sure to have a value for MAC address, you can use the icon on the right to generate a new MAC address for the virtual network card.

enter image description here

  • I was wondering about that, too. My VM definitely has a MAC address though - I even clicked the "generate new MAC address" & restarted it & it still doesn't work. Nov 25, 2012 at 1:03
  • Why not try to delete the VM (keeping the VM disk I guess) an re-create it ?
    – jhcaiced
    Nov 25, 2012 at 1:21

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