We recommend the use of VirtIO (QEMU/KVM), which is deployed as default with any newly created server and is is widely supported in modern operating systems.
If you are running a relatively old OS, such as Windows XP, the Realtek RTL8139 is an older model which should be supported by your OS.
You can modify the networking server on a non-running server, by first selecting the server from ‘My Servers’.
From the ‘Network’ tab select the orange ‘Edit’ button to modify the networking resource.
From the ‘NIC model’ drop down select the networking card desired.
Click on ‘Save’ and proceed with the configuration or running of your server.