To play GTA 4 online you’ll need stable connection with dedicated IP address or you have to make the needed modem settings. So you’ll need the Bridge mode, remember it because with another mode it won’t be started.
In the modem settings change distribution of the computer channel on one. The usual modem position is Routing, but you need – Bridge. Save these changes and start the registration. After the registration you can renew or modify the game version with patches. Install them in the order specified.