After the install there is only a Loopback-Pseudo-Interface shown when I execute
netsh interface ipv4 show interfaces
Do I have to enable the real adapter explicitly or does the server has no appropriate driver for the network adapter?
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, see the FAQ.
As jscott said, you really need to provide more info (make/model) of the system and the NIC. That being said, if this is server class hardware and you just ran the install directly off a Microsoft retail/Volume license media, it's a pretty good bet that you need to get the driver for the NIC. If you have drivers you can install them in core using the pnputil.exe
edit: wow - just realized this question was from 2011 but only edited again today. Somehow, I doubt this user is coming back to mark this as answered..
Try "netsh interface set interface name="Local Area Connection" admin=ENABLED" just to see if can ressurect the adapter. If not, it would seem they are not appropriated from the bios.