It's true what SAABoholic writes, but you can acces the controller on your factory network via the serviceport as long as you only got 1 controller on the network because you can't chance the IP settings for the service port, otherwise you can get a converter you plug directly on the serviceport and to an outgoing internet connection, i use that a lot of places where i need to go online on robots without PC interface.
The correct way is however:
Get the option PC interface
Reboot the system with the new key.
X-Start the system (hit ABB/Restart/Advanced/X-Start) select fixed IP and enter IP, Subnet, gateway.
Put the cable from your factory network in LAN on the main computer (not the serviceport)
This i for RobotWare 5, on 5.6 and 6 you got multiply Lan on the new main computer (DSQC1000) so there you need to set the right one up.