Unix: How to "refresh" network connections

Question

I have a VM running Ubuntu and I'm experimenting with the various networking options. The problem I have is that I don't know how to get Ubuntu to "refresh" the network connections after I have "unplugged a network cable" and "plugged in a different one". Only way I get it to work now is to reboot the VM which is a bit annoying.

It's using the server version of Ubuntu and I don't have a GUI, so I would like to know how to do this in the terminal.

Solution

You can restart networking as a whole or just the NIC (assuming eth0 - change to match your adaptor name) - as follows:

General networking restart

/etc/init.d/networking restart

NIC restart (on the console - ie: not remotely):

  ifdown eth0
  ifup eth0