Bridged networking in OpenSUSE 10.3 & 11.0 (For VirtualBox)

I prefer to use VirtualBox rather than VMware as it seems to be rather faster and less resource hungry than VMware Server (the only free version of VMware with a GUI). Also VirtualBox seems to have better Linux host support (sound, etc.).

However, there is one thing that VMware is better at – setting up the guest network on the same network as the host.

Under VirtualBox this is called “Host Interface Networking” and, with a Linux host anyway, is a right royal pain to set up. This is because VirtualBox uses the powerful and flexible bridging capabilities of Linux – but they have no easy GUI setup!

So here is my summary of getting host interface working on my OpenSUSE 10.3 desktop. Firstly though, note that I have two network cards. I am not going to mess with eth0 as this is the card I use for the main network from my desktop. Instead I am going to configure eth1.

  1. Install the package “bridge-utils”
  2. Follow the instructions at the OpenSUSE web site to set up a basic bridge. You will end up with a new file in /etc/sysconfig/network called “ifcfg-br0” containing something like:
    ## Bridge 0 config - to allow VirtualBox to use
    ##    Host Interface Networking mode with eth1
    
    STARTMODE='auto'
    BOOTPROTO='static'
    # Change the above to dhcp to use your networks
    # dhcp server to assign an address
    # (the next 2 lines are then ignored)
    IPADDR=192.168.3.1
    NETMASK=255.255.0.0
    # Note that the above puts the bridge onto a different
    # subnet to my main network but that I use class B
    # addressing to ensure everything can talk
    NETWORK=
    BROADCAST=
    STARTMODE=auto
    USERCONTROL=no
    NAME='Bridge 0'
    NM_CONTROLLED=no
    BRIDGE='yes'
    BRIDGE_PORTS='eth1'
    BRIDGE_AGEINGTIME='300'
    BRIDGE_FORWARDDELAY='0'
    BRIDGE_HELLOTIME='2'
    BRIDGE_MAXAGE='20'
    BRIDGE_PATHCOSTS='19'
    BRIDGE_PORTPRIORITIES=
    BRIDGE_PRIORITY=
    BRIDGE_STP='on'
    
    

    I think that you may also need to tell the bridge where your default router is. Create a file in the same place as above called ifroute-br0 containing:

    default 192.168.1.1 -
    

    (or whatever your router is).
    Then, when you’ve done a “/etc/rc.d/network restart” as sudo, you should see that eth1 and br0 both come back up.
    Note that it is possible that you have to change eth1 to give it a manual IP address of 0.0.0.0, netmask 0.0.0.0 for it to work correctly (as per the instructions in section 6.7.1.2 of the VirtualBox manual – note that some of the rest of those instructions seem to be incorrect). Note that SUSE 11.0 at least has a setting for this in YAST (edit the card config and select none for address assignment).
    The ethernet card eth1 is now indirectly used via the bridge br0.
    Here is my ifcfg-eth1.

    BOOTPROTO='static'
    BROADCAST=''
    ETHTOOL_OPTIONS=''
    IPADDR='0.0.0.0'
    MTU=''
    NAME='ASUSTeK Marvell 88E8001 Gigabit Ethernet Controller (Asus)'
    NETMASK=''
    NETWORK=''
    REMOTE_IPADDR=''
    STARTMODE='hotplug'
    USERCONTROL='no'
    

    UPDATE 2008-07-18: In addition to the above, you must create a default route – but don’t do it via YAST! YAST has a bug that often deletes the default route. Instead, put the following line in the file “/etc/sysconfig/network/routes“:

    
    default 192.168.1.1 - -

    Note the two dashes at the end

  3. Create a permanent interface for VirtualBox to use (also called a “tap” interface) with the command:
    sudo VBoxAddIF vbox0 <user> br0
    

    Where is the VirtualBox user running the VM – I guess you have to do this for every user who might run the VM.
    If you run the command “ifconfig” you will now see a new network interface called vbox0 which will reappear along with br0, ethx, etc. every time you reboot.
    Note that these VirtualBox interfaces can only be used once so if you have two VM’s, you will need two interfaces. Also note that VirtualBox has a method of creating dynamic interfaces (that only appear when you want them) but that is more complex to set up.

  4. Now tell your VM configuration to use this interface.
    You can do this via the GUI by putting the required name (vbox0) into the network settings box “Interface Name” under the HIS section. Or you can do it with the command:

    VBoxManage modifyvm "My VM" -hostifdev1 vbox0
    
  5. Make sure that the guest OS is running the network connection with DHCP so that it gets the correct address, gateway, DNS, etc.
  6. You might need to set a default gateway in the host OS.

Job is done!! After some years of attempting this on and off, it has finally come together and all works. Hopefully this little list is enough to get you going.

Regards, J.

UPDATE 2008-08-12: It seems that there is something slightly amis with the above instructions. On reboot, the network is not quite left in the correct state and you have to do a “/etc/rc.d/network restart” before host networking will actually work.

UPDATE 2008-08-22: Oops, sorry but I got the addif command wrong, it was missing the userid bit. Rats! Blogger keeps eating the < symbol.

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  • Julian

    And one final update!

    You no longer need to go through all of the above messing about. The latest versions of VirtualBox simply work! Select Host Networking and choose a network interface – done.

    This works for both Windows and LINUX.

    Regards, Julian.

  • Julian

    I’ll post my own comments as it saves me editing the article all the time.

    You can use the command: “brctl show” (as root) to see if the vbox0 virtual network card is actually attached to the bridge.

    You can also use the command “netstat -rn” (as root) to see whether you have the correct default routes.

    Rather than adding a global default route, you can add default routes to each interface. I added them to eth0, eth1 and br0. Doing this enabled me to have the default external traffic going through eth0 which is what I wanted (with vbox traffic going through eth1/br0) – using a global default pushed everything through the bridge for some reason.
    The files are called ifroute-eth0, ifroute-eth1 and ifroute-br0 and all contain:
    “default 192.168.1.1 – “.

    Regards, Julian.