Why Wired Internet is not working in Ubuntu 16.04 LTS?

You know, I was waiting for this release from last 3 months eagerly. I even downloaded it through torrents to help in anyway I can.

When I installed it and I saw that it doesn't recognized my broadband connection. I installed it on another hard disk (I had two). Then I booted to my Windows 7 again and Internet was working. Then I booted to Ubuntu 16.04 again and there is no Internet. When I saw available connections, it showed Network 1 or I don't know what but something was there; but no IP address.

The main point to note is, when I was seeing these available connections. I tried to delete that single connection it was showing. It got deleted. When I booted into Windows 7, it also stopped recognizing any connection. Troubleshoot was always showing that "there is no cable connected" but it was there! The cable was connected and 100% working on my router! Seems like because I deleted that 'shown connection' in Ubuntu, it did something weird to my hardware. In frustration, I wiped out Windows 7 and reinstalled it; clean. But still not recognition of cable connection.

Next day in evening when I again started my computer, Internet started working again (Thank God). But now it was showing "Network 2" instead of any other name. And it was also connecting and disconnecting automatically. For now because 2 days has passed, it seems stable.

Now I want to know what actually happened? I really wanted to install Ubuntu 16.04 and wanted to use it as my primary OS.

So I read somewhere on this forum or I don't know where that a user having similar problem cold booted his computer and internet worked or did I read somewhere that cold booting removes everthing from ROM or RAM (I don't know)? I did the same about 2 days ago and to my surprise, internet worked! Ubuntu 16.04 detected wired connection and it started working. Yay!

so disabling ipv6 was only part of the problem.

this got everything working for me:

sudo sh -c "echo 'net.ipv6.conf.all.disable_ipv6 = 1' >> /etc/sysctl.conf"
sudo sh -c "echo 'net.ipv6.conf.default.disable_ipv6 = 1' >> /etc/sysctl.conf"
sudo sh -c "echo 'net.ipv6.conf.lo.disable_ipv6 = 1' >> /etc/sysctl.conf"
sudo sysctl -p
sudo sed -i 's/false/true/g' /etc/NetworkManager/NetworkManager.conf
sudo reboot -i NOW