I upgraded the first of our iMacs to High Sierra on Friday. Unfortunately, the Ethernet is now having serious problems that weren't present before the upgrade. Running a ping test from one of my Linux servers to the Mac results in 25%-35% of the ICMP packets not getting a response. The network seems to be non-responsive for about 30 seconds, then responsive for about 90 seconds, then non-responsive for another 30 (it is not completely regular, but I hope you get the idea).
This reminded me of the Ethernet problem we had with Mavericks a while back, so I tried both a Thunderbolt to Ethernet adapter as well as a USB to Ethernet adapter. They both showed the same symptoms as the internal Ethernet.
Has anyone seen something similar?
