Late 2011 iMac 27" connected to Time Capsule via Ethernet cable. After updating to Sierra, I have lost the ability to connect to the Internet despite network diagnostics showing all elements as working. I can even ping websites successfully using Terminal with no packet loss. My machine has no WiFi unit, so the early 2016 kernel issue after the security update does not apply and I have the latest one. Tried several different DNS servers, turned firewall off and even tried plugging into cable modem directly after rebooting it. Nada! When I restored back to El Cap, everything works fine again. Sierra just seems to be blocking something! Any further ideas?