This networking mode enables you to interconnect virtual machines running on different hosts.
Technically this is done by encapsulating Ethernet frames sent or received by the guest network card into UDP/IP datagrams, and sending them over any network available to the host.
UDP Tunnel mode has the following parameters:
Source UDP port: The port on which the host listens. Datagrams arriving on this port from any source address will be forwarded to the receiving part of the guest network card.
Destination address: IP address of the target host of the transmitted data.
Destination UDP port: Port number to which the transmitted data is sent.
When interconnecting two virtual machines on two different hosts, their IP addresses must be swapped. On a single host, source and destination UDP ports must be swapped.
In the following example, host 1 uses the IP address 10.0.0.1 and host 2 uses IP address 10.0.0.2. To configure using the command-line:
VBoxManage modifyvm "VM 01 on host 1" --nic<x> generic VBoxManage modifyvm "VM 01 on host 1" --nicgenericdrv<x> UDPTunnel VBoxManage modifyvm "VM 01 on host 1" --nicproperty<x> dest=10.0.0.2 VBoxManage modifyvm "VM 01 on host 1" --nicproperty<x> sport=10001 VBoxManage modifyvm "VM 01 on host 1" --nicproperty<x> dport=10002
VBoxManage modifyvm "VM 02 on host 2" --nic<y> generic VBoxManage modifyvm "VM 02 on host 2" --nicgenericdrv<y> UDPTunnel VBoxManage modifyvm "VM 02 on host 2" --nicproperty<y> dest=10.0.0.1 VBoxManage modifyvm "VM 02 on host 2" --nicproperty<y> sport=10002 VBoxManage modifyvm "VM 02 on host 2" --nicproperty<y> dport=10001
Of course, you can always interconnect two virtual machines on the same host, by setting the destination address parameter to 127.0.0.1 on both. It will act similarly to an internal network in this case. However, the host can see the network traffic which it could not in the normal internal network case.
On UNIX-based hosts, such as Linux, Oracle Solaris, and Mac OS
X, it is not possible to bind to ports below 1024 from
applications that are not run by root
. As a
result, if you try to configure such a source UDP port, the VM
will refuse to start.