Thank you for your answer.
At the moment, the server and the client from which I manage it are not connectet to the productive network,
that means there is no firewall at all between these two computers. The nics are linked directly with two crossover cables.
I have added some routes on the client and tried many different IP-settings on the client nic, but nothing helped so far....
I can't remember if I testet a route from 172.16.10.x to 172.16.0.x yet, I'll give it a try