Ubuntu 16.04 Ethernet issues
I found a workaround for anyone who might be having the same issue. No idea what the actual problem is but it seems as though setting the IPv6 settings "Method" section to "ignore" has resolved it.
Not sure if this will work. I also had this problem till I changed my Internet DNS servers to 8.8.8.8,8.8.4.4. Changed it for the IPv4 and it started working very well. Make sure you enter the values properly.