I had network connectivity working in ubuntu 12 under virtual box.
I issued the commands
sudo ifdown eth0
sudo ifup eth0
and now ubuntu no longer can connect to the internet. I'm not very familiar with this. How can I fix this issue?
Try
sudo ifconfig eth0 down
sudo ifconfig eth0 up
sudo dhclient eth0
Otherwise, turning the VM iff and then back on will do.
Have you tried doing the following?
sudo service network restart