I have upgraded from 12.2 to 12.3 but my eth0 device starts only manually with ifconfig eth0 192.168.92.11 and route add default gw 192.168.1.1. I have networkmanager installed but I cannot find it. How can I fix this?
It seems like you are not running network manager and using ifup / ifconfig instead.
In yast under network settings go to "Global Options", in that tab there will be a way to swap between Traditional (ifup) and Network Manager, having selected network manager you will then be able to configure it as you desire.