Intel I217LM ethernet controller not detected by Ubuntu 12.04LTS
Solution 1:
This appears to be a real fix.
I had the same problem today and found the explanation: support for Intel I217 is available since linux kernel 3.5 (commit). As Ubuntu 12.04.2 uses kernel 3.2.x, the Ethernet card is not recognized and cannot work.
I followed your advice and installed the e1000e driver from the Intel e1000e drivers page and it worked perfectly. From there I was able to upgrade the linux kernel.