I am working on a network driver where there is one physical ethernet but am creating more than one logical interfaces being serviced by the same driver. I am able to create the primary interface without problem after using register_netdev. The logical ones cause the system to hang as soon as registration is done. However if I use register_netdevice, I face no problem in creating the device. But in that case, ifconfig does a segmentation fault. Only after removing (unregistering) the newly created logical interface does ifconfig work without a crash. I am using kernel version 2.6.12.