I recently ran into a situation where a Linksys WRT-54G wasn’t able to get an IP address when connected to an Ambit/uBee U10C018 cable modem. This issue may also apply to other routers when used with the U10C018 cable modem.
When a PC is connected directly to the modem, everything works fine and the Internet can be reached normally. When a router is placed inbetween, then there is no longer any access to the Internet. Viewing the status information in the router shows that it is unable to acquire an IP address, even though the router is set to use automatic configuration via DHCP, the same as the PC.
Apparently, the U10C018 cable modem is aware of the MAC address of various routers. In order to get the router to work with the modem, use the MAC cloning feature of the router. The location of this option will depend on your particular router brand and model. When you find it, turn it on. Then, set the desired MAC address.
On the Linksys router, the MAC address cloning page has a button to copy the MAC from the PC that’s currently connected to the administration interface. If your router has this feature, use it to set the router to the same MAC address as your computer. If your router does not have this feature, then you’ll have to get your MAC from the network driver or the network card.
Once you have a non-router MAC entered into the MAC cloning setting, save and restart the router.
Have you run into this issue? If so, post your router model and steps to configure MAC cloning for it in the comments.