hello, i have been trying to connect Cisco 1720 router to time-warner cable modem for home network. the router has two ethernet ports, fa0 and eth0. i want eth0 to be internal and fa0 to connect to modem. i enabled dhcp on fa0, but the cable modem always gives a private IP instead of public. time warner has no idea how to fix this. their response was that for some reason the modem thinks that the router is one of their network's nodes.
i would really appreciate your response.
AFAIK, the cable modem should only hand out a private IP if it doesn't have upstream connectivity to its head end. Are all of the proper lights lit on the modem before you attach or power up the router? If you connect a PC directly to the modem, does it also acquire a private IP? In what order are you powering up your equipment? The cable modem has to be powered up first (or power cycled if already running), followed by the router after the cable modem has settled down. I don't know anything about the 1720 but if everything works with a PC directly connected, then I would look to the router for answers.
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