The above didn't solve it for me. Someone else had the same problem
google windowssecrets dot com Windows-10-Realtek-PCIe-GBE-Family-Controller-Intermittent-ethernet-disconnect
or this icon might work for you:
Suggestion its "Realtek RTL8411B-US Ethernet Controller Driver" -and dells drivers listed are outofdate
On my problem machine Device Manger - Network adapters - Realteck PCIe GBE Family Controller - Ethernet Properties driver says its "realtek PCIe GBE Family Controller" version 10.1.505 2015 - driver date 5/5/2015
Solution download latest driver realtek.com.tw - Downloads\DellDrivers\Install_Win10_10008_05202016
This installed a driver 10.8.31 2016 Driver date 3/11/2016 and worked.
Then to make sure, I unisntalled, rebooted - it discovered it and reinstalled it - and now the networking is good.
Whew! so appears the Dell Download drivers downloaded are out of date.