Issue: Unable to Obtain an IP address even when the Cable Modem is online and has what appears to be a good signal after a customer switched either the ethernet card in the PC or hooked up a new computer (PC or Macintosh).
Solution: Clear both the Ethernet and Cable Modem MAC id's on the UBR in the NOC tools.
Why does this happen? Charter, and many other ISPs have the cable modem configured to recognise only one client PC. Once the cable modem has learnt the MAC address of the first PC that talks to it, it will not respond to any other in any way.
Thus if you swap one PC for another, the new PC will not work with the cable modem, because the new PC has a different MAC address to the old one. To reset the cable modem so that it will recognise the new PC, you must power the cable modem off and on again. Once the cable modem has rebooted and gone fully online again (indicator lights settled down), reboot the newly connected PC so that it makes a DHCP request.
With some ISPs, it appears that, although resetting (or power cycling) the cable modem is enough to clear the table of learnt MAC addresses in the cable modem, it is not enough to force the ISP's DHCP server to lease an IP address to the newly connected PC. It is suggested that, before the first PC is disconnected from the cable modem, it should release its DHCP lease.
In Windows 9x/ME, this is an option in the winipcfg command. In Windows 2000/XP, type the command ipconfig /release. If even that is not enough, it might be necessary to wait for the expiry time of the original DHCP lease, and then reset the cable modem again.If both old and new PCs are connected by USB to the cable modem, then these problems do not arise, because the USB driver software emulates an ethernet MAC address, and that emulated MAC address will be the same in both cases, so the cable m odem does not notice the change.
All that is necessary is to release the DHCP lease on the old PC, change the USB cable to connect the new PC to the cable modem, and request a DHCP lease on the new PC.
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