DHCP/DNS issue: Couldn't access NetPI3 out-of-the-box

[Armin@netPI]

Another possibly related question: In one of the forum posts you mention the Tcp/Udp ports opened by the NetPI3. According to that post, bonjour is running as well. Why? Can it be used as another option to initially access the NetPI3?

Yes you can use a detection function across the bonjour service as well. I tested a detection with a scanner software from company Hobbiyst Software. It works pretty well. It is available for multiple OSs, I tested the Windows version.
If you are in a company network and your network mask is about 255.255.0.0 the scanning procedure take long long time. So make sure you are in a 255.255.255.0 network. Then it is pretty fast.