ok the following is taken from NTL's website.
So if the modem has no internal IP address what are NTL on about here? I dont mean to sound rude or anything, i am just confused
Finding the cable modem's address
Most DOCSIS cable modems have two IP addresses:
- a customer-side IP address used on the ethernet/USB socket to which the user connects;
- an ISP-side IP address used on the CATV socket to which the ISP's network connects.
The customer-side IP address of a DOCSIS cable modem is normally
192.168.100.1. For 3Com Tailfins with early firmware versions it was
149.112.50.65. Firmware can be automatically updated by your cable operator down the cable, so by the time you read this, most Tailfins will have been updated to use the standard address. The 3Com CMX does not have a customer-side IP address.
The IP address
192.168.100.1 will be present even if no web diagnostics are offered on that address.
The cable modem IP address
192.168.100.1 is not in the same sub-net as the user's PC. So, when trying to send to
192.168.100.1, the user PC's IP stack will normally route the packet to the Default Gateway address at the UBR. Since no routes exist to the private address
192.168.100.1 (and there are multiple instances of this IP address on any one CATV segment), the UBR drops the packet. This would mean that in theory the PC could never talk to the cable modem. However, the Surfboard, the 3Com Tailfin, and the ntl:home 100/120 are capable of sniffing the passing traffic through the transparent bridge to intercept any packets addressed to themselves. This only works when the bridge is open, so the cable modem diagnostics cannot be read when the cable modem is booting up or failing to remain in contact with the UBR.
Thanks
Neil