virtualbox.org

Using 3.2.8 on Windows 7 64 bit host, guest is Windows XP SP3 32-bit.

Port forwarding doesn't work, I set it up using new syntax :

VBoxManage modifyvm "vm01" --natpf1 "rule01,tcp,,50000,,50000"
VBoxManage modifyvm "vm01" --natpf1 "rule02,udp,,51000,,51000"

Using the same guest mounted on VirtualBox 3.1.8 on the same Windows 7 host, it works great using this configuration:

VBoxManage setextradata "vm01" "VBoxInternal/Devices/virtio-net/0/LUN#0/Config/rule01/Protocol" TCP
VBoxManage setextradata "vm01" "VBoxInternal/Devices/virtio-net/0/LUN#0/Config/rule01/GuestPort" 50000
VBoxManage setextradata "vm01" "VBoxInternal/Devices/virtio-net/0/LUN#0/Config/rule01/HostPort" 50000

VBoxManage setextradata "vm01" "VBoxInternal/Devices/virtio-net/0/LUN#0/Config/rule02/Protocol" UDP
VBoxManage setextradata "vm01" "VBoxInternal/Devices/virtio-net/0/LUN#0/Config/rule02/GuestPort" 51000
VBoxManage setextradata "vm01" "VBoxInternal/Devices/virtio-net/0/LUN#0/Config/rule02/HostPort" 51000

Also I've tried with 3.2.0 and 3.2.6, but I have the same problem

If you use a router to connect to the internet, instead of having a direct connection, why not use bridged instead?

Bridged network will work.