usb0 network interface doesn't get up

I have connected an embedded board to a usb0 interface of a Linux machine to establish a ssh connection to it. ifconfig tells me: usb0 Link encap:Ethernet HWaddr 16:43:4D:AA:E8:5A inet addr:192.168.2.5 Bcast:192.168.2.255 Mask:255.255.255.0 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) But it is not "RUNNING". How can I start the interface? Is there a driver missing? lsusb finds the device. The device itself runs Yocto Linux.