what is the correct way to restart network on the command line

[Wes James]

I've tried:

sudo /etc/init.d/networking restart

but get a deprecation error

I googled this and it seems to have changed to:

sudo ifdown eth0
sudo ifup eth0

but when I do that I get "interface eth0 not configured"

I look in:

/etc/network/interfaces

and all it has is:

auto lo
iface lo inet loopback

no eth0?

where can I study up on networking on 11.04?

The indicator in the Gnome menu bar can disconnect/reconnect
connections or turn networking off or on - is it using scripts to do
this work?

Thanks,

-wes