UD-3900 Ethernet cannot use DHCP to get an IP address. On MacBook Pro (Retina, 15-inch, Mid 2015) running OS X Yosemite. Plugable DisplayLink drivers installed and working. Plugable UD-3900 Ethernet interface available and added to network settings.
For reference: USB ethernet adapter plugged into USB 2.0 port is working on the same Ethernet line. All display ports (HDMI, DVI) working. All USB ports (3.0 and 2.0) working. Drivers installed June, 2016.