how to restart network with NetworkManager controlled wired connection

[Antonio Olivares]

Dear fellow testers,

If I want to stop students from accessing the internet at school with one of the testing machines, I use

# service network stop

and the network stops and will not connect to internet anymore.  Restarting fixes it back.  However if I do not want to restart, I try

# service network start/restart

I won't get the connection back.  How do I get the connection back if NetworkManager is running and I previously stopped it.  I just want to know if it is possible.  

TIA,

Antonio