Trying to run 5.1.1 or 5.1.0 either from CD or HD (debian install) runs fine, but network connection is failing. It looks to me that the eth0 is in fact recognised (pls how to verify?) but when I try to make any connection it does not work. Asking for DHCP will broadcast for a while, but says then failed, but what I dont know.
Manual settings failed too, I tried to take a fixed IP from our network, typed all numbers in, ifconfig confirms that, but not even a ping seems to go outside. Ping says not reachable and is not detected in units in the same subnet.

what is then missing or can I find some logfiles somewhere?

Sorry, but I am not so much familiar with linux.