I am attempting to place an Ubuntu server (11.04) on our Class C Active Directory (Server 2003 R2) network. I want this server to have a static IP, which I've selected from outside the DHCP pool, but I am not interested in joining the server to the domain properly; it just needs to be available to provide services to local clients that are pointed at it. I set up /etc/network/interfaces correctly, it responded to pings at that address, I rebooted and was able to subsequently ssh in from another client on the network. Great. At this time it was sitting in the same room as the other client (my workstation, on my workbench), going up to the server room and back down again, presumably. After taking it upstairs and plugging it directly in to two (2) of the switches in the server room (successively, not simultaneously), the lights on the port it was plugged into would consistently flicker during boot, but would go dead by the time the logon prompt has appeared, and would remain so thereafter, for any number of reboots (on both switches). So, I brought it back downstairs, plugged it back into my workbench, and...it's not picking up the network now, can't see other hosts (including the default gateway), can't see google, doesn't respond to pings... WHISKEY TANGO FOXTROT, MAN? I am learning a lot as I go in this job, and am definitely no CCNA, as this post almost certainly makes clear. But this seems all funhouse mirror to me, and I've spent the last couple of days trying to google up enough information to understand exactly what I should be googling to get the answers I need. It's not working.
Please forgive the length of this "question," which I suppose could be summarized as: A.) is there a clear, distinct problem domain that this issue lies in, which I could be focusing intently on to identify the solution, or B.) if not, what are the broader subject matters (not too broad; for goodness sake don't say 'networking') that I should be researching to narrow my problem down?
Thanks very much in advance for any direction you can provide.