I have a very strange problem with networking, I have my internet connection via a cable modem, Motorola SurfBoard 4100 trough usb in a windows xp pc of my family and on ethernet in my machine. Every time I change the etehrnet card I have to disconnect the cable modem from the power and connect it again for it to work with the new ethernet card. A pretty strange problem, now the biggest problem is I changed to a integrated lan in my mobo. Since that happened I had no internet on windows nor Linux even tough the ethernet driver was configured. I had do disconnct from power several times the cable modem and at last when I turned both computers off and the cable modem as well and then turn on the cable modem then my pc and then the other pc, only doing that the internet conection started working on windows and then I installed pcbsd and it worked too, but this morning it worked on windows but not on pcbsd nor any linux distro. After disconnecting from power the cable modem it didn't worked either just on windows but then I disconnected the lan cable and reconected while in windows and quickly reboot and it worked on pcbsd and linux, but when I rebooted back to windows and then back to pcbsd and linux it was not working on the latests but it was on windows. Let's discuss this, Thanks. any more input will be given when asked. I have to add the connection is obtained via dhcp.

Is there any reason you are using the USB cable and not the ethernet cable?

This is a very common situation with cable Internet. Most cable ISPs use the hardware MAC address of the computer's network adapter as a form of authentication, so if you connect a different device to the modem, it won't work. You need to power cycle the modem a few times so it forgets the previous MAC and re-authenticates with the new device connected to it.

This will happen anytime you switch between the family computer and your computer, and also between the network cards on one computer (you mentioned switching over to the onboard NIC on one of the machines).

The only practical way to avoid this is to purchase (or build out of an old machine) a router that will present only one MAC to the modem while allowing multiple machines to simultaneously connect to the Internet.

Ok I see, still the usb coneccted machine is of my family and my maching is through ethernet, both computers are used at the same time, and now I have my cable modem kind of working, kind of I say becuase it is working with windows only on my ethernet lan machine but not on linux or bsd, and is strange since it started working with linux and bsd for a few hours and after I logged to windows and then back to bsd and linux it stopped working on linux and bsd but still works on windows. Is very frustrating.

Ok, this is getting very strange I'm going trhough the power cycle on my cable modem still my connection only works in windows and not in linux. Does anybody has a hint of why this happens? After some power disconnects and connects of my modem I sometimes get the connection to work on linux via my onboard lan but as soon as I logg back on windows and return to linux or if it was working on linux and I boot to another livecd of linux my connection stops working on Linux but not in Windows. This is the strangest thing.