The ip address assigned to your PC is linked to the mac address of the device that is connected. A USB connection will always have a mac address one digit higher than the mac address of the cable modem, whereas an ethernet connection uses a NIC which has it's own mac address. The way to force an ip to change is to change the mac address in one of the following ways:
- switch from usb to ethernet or vice versa
- change network cards
- change the mac address of the NIC; Instructions (for windows):
Go into device manager and then the properties of the network card. In the "advanced" section there is an option to change the network address/ physical address/ mac address. Check the current mac address using ipconfig /all from a command prompt and then increase the mac address by one digit. Reboot everything and you should have a new ip.
You can also change a mac on an Apple Mac that is running 10.1 or higher using terminal, and typing:
sudo ifconfig en0 ether 00:00:00:00:00:00
where en0 is the interface you are using, and the zeros are the mac address that you want to use.
And for all you linux munkehs.... when logged in as root use:
/etc/init.d/networking stop
ifconfig eth0 hw ether 00:00:00:00:00:00
/etc/init.d/networking start
then reboot
Leaving the connection off for a period of time does not guarantee the same ip address, because even if the lease has expired, if the ip address has not been assigned to someone else you will get the same ip back again. Also reinstalling the ntl software will not give a different ip unless you use a different device to connect.