If after a upgrade from Ubuntu 14.04 to 16.04 you notice that networking did not come back online please reference the steps below:
systemctl enable systemd-networkd
systemctl enable systemd-resolved
systemctl start systemd-resolved
ln -s /run/systemd/resolve/resolv.conf /etc/resolv.conf
- Add the following:
[Match] Name=e* [Network] DHCP=yes
After this is completed restart the server and networking should be back online.
If it did not come back online after this run
This will determine if your interface name has changed from eth0 to something else. If this is the case then you will also need to edit /etc/network/interfaces and replace references to eth0 with the new name.