I spent an entire morning tracking down this issue. I got an ethernet cable to connect my personal server to my router so that I could use the wake on lan feature to save power. Getting wake on lan to work was easy, but the problem was that the server couldn’t acquire an IP from the dhcp router after it woke up from sleeping. Win 7 would attempt to discover the network but would fail and give an “Unidentified network” message. Releasing and renewing the IP didn’t work. The only way to get it connected to the network again was to disable/re-enable the LAN adapter. Can’t exactly do this remotely. So I added my dhcp router to the default gateway list in the ipv4 item in the LAN adapter properties. Then it worked!!
Some say to disable the “All windows to put this device to sleep to save power option”. But I needed that option checked to have WOL to begin with.
Another problem tracked down and solved!