A couple of years ago I installed Cat5 cable under the house ending in wallplates with ethernet receptacles. My Airport router is located about 75 feet away from my Mac Mini on the other side of the house. Will try to explain here for others who may be having similar problems. I started having problems again and did some additional troubleshooting. Glad to hear you are not having problems since you upgraded. The odd thing about this experience is that Network Diagnostics could not determine the cause of the problem and Network Preferences showed 'Ethernet is currently active and has the IP address 10.0.1.XX'. Unplugging the ethernet cable from the Airport Extreme to the ethernet switch seems to have reset a connection even when a power cycle of the switch alone did not work. So I re-connected the ethernet switch in between the Mac Mini and the Airport Extreme and everything now works normally. But I need to use the ethernet switch for other devices in the room. Finally, I connected the ethernet cable from the Airport Extreme directly to the Mac Mini without going through the ethernet switch and everything was back to normal. I tried a power cycle on the ethernet switch but still had the problem. I have an ethernet switch in between my Mac Mini and the Airport Extreme. I suspected the problem was with the ethernet network configuration on the Mac Mini but had no success trying different configurations. So, there did not seem to be a problem with the Mac Mini or the Airport Extreme. In addition, other devices connected via ethernet in other rooms connected to the Internet normally. However, if I turned Wi-Fi on in Network Preferences the Mac Mini connected to the internet without a problem. Followed many suggestions in this support community to restart the Airport Extreme, renew DHCP lease on the Mac Mini, etc.

The odd thing is that Network Diagnostics indicated green dots for Ethernet, Network Settings, and ISP but the Internet and Server dots were orange/yellow.

One morning I could not connect to the internet. Connected via ethernet to an Airport Extreme router. I have a Mac Mini, mid 2011, running OS X 10.10.3. I benefited greatly from many of the suggestions in this support community but none of those posts identified the problem. Spent hours troubleshooting an internet access problem and thought I would post for others who might have a similar experience.

Mac ethernet no internet