Connecting RPI to a Virtualbox Linux VM in a protected network

Question

I'm on a protected network which only gives IP addresses to registered devices. I can register my laptop, a Windows machine, and a RPI, but not every VM on that laptop, so bridged adapter is not an option, I think. I'd like to be able to communicate between the RPI and the VM.

So far I have tried this:

I have 3 entities: (1) A Windows host, with IP 134.58.46.117 (2) A Virtualbox Linux Guest VM, configured, atm, with NAT network and a Host-only Adapter. it has IP 10.0.2.15 on eth0 and IP 192.168.56.102 on eth1 (3) a RPI on Jessie, with IP 134.58.46.172 on eth0.

I can ping 192.168.56.102 from the Windows Host. I can ping the Windows Host from the RPI. I can ping the RPI from the Windows host. I have configured the RPI with the following route:

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.56.0    134.58.46.117   255.255.255.0   UG    0      0        0 eth0

When I ping the VM from the RPI ( so execute "ping 192.168.56.10"), I receive no response.

Wireshark on the Windows host does detect packets from 134.58.46.172 with destination 192.168.56.102 however, but nothing is returned.

Any clue what the issue is? Or another way to do what I want?

Answer 1

You need two steps for this to work:

1. First, you need to allow IPv4 forwarding on the Windows machine. This will allow it to move packets from one interface to the other. The instructions to do this depend on the Windows version you are using, for instance for XP you can use this reference and for Windows 10 you can use this other reference. At any rate, Google Windows YourVersion IPv4 forwarding for more info. In any case, it is just matter of changing a Windows Registry entry, albeit the exact key changes with Windows version.

2. You need to instruct your Linux machine to use the Windows host as a gateway for the RPI. It can be done with the following command:

   ip route add RPI_IP_ADDRESS/32 via WINDOWS_HOST_IP_ADDRESS
   

   This makes sure that packets can flow in the opposite direction with the headers of the Linux VM guest: this way they are recognized as the pertinent reply to conversations started by the RPI. If you did not use this, the packets headers would be changed to reflect the Windows host IP address, which means the RPI would receive replies froma different address than the one it had written to.

That's all.

EDIT:

with reference to the comment:

give your Linux guest a fake MAC address, one which has access to your LAN. Use the RPI to listen on conversations, with tcpdump -i eth0 -n arp. This will display a number of MAC addresses which are present on your net. Change the MAC address of your Linux guest with macchanger, giving it the one you just learned. Now use Bridge adapter for the Linux guest. It will work like a charm. Also, you might consider getting a pc with a real OS, since what you are trying to do is quite sophisticated. Windows falls short there.

1. stealing an address does not interfere with the other guy's connectivity: packets are numbered, if your pc receives a misnumbered packet it will simply discard it.

2. you make it permanent on boot as follows: on the VM (I assume you are on Debian or derivatives Ubuntu/Mint,..., if not it is a synch to adapt what follows to whatever you are on), edit /etc/network/interfaces, and paste the following in (assuming eth1 is the interface to connect):

   auto eth1
   iface eth1 inet dhcp
            pre-up macchanger -m XX:XX:XX:XX:XX:XX eth1
   

and that's it.