Webstar Cable Modem & Netgear DG834G

malice05 · 03-02-2007, 22:34

Hi,

I am trying to remotely diagnose my daughter's internet set up with an NTL cable modem together with an ADSL Wireless router acting as a plain wirelss connection point.

If her laptop is connected via her wired ethernet connection and has AUTO assign IP DNS (on XP), the laptop can connect to the internet fine. In this configuration her default gateway is 82.XXX.XXX.XXX (can't remember it exactly).

When her laptop is then substituted with the NEtgear router, she can wirelessly connect to the router (confirmed by access to the router's ip of default 192.168.0.1 and the web configuration interface). In the NEtgear we have turned off DHCP, enabled RIP in both directions with 2b as the version. But her laptop cannot connect to the internet.

I thought the cable modem may have had a configuration page where you could manage the IP ranges assigned on the ethernet port, but I don't think there is one. If the laptop was being assigned an 82.xxx.xxx.xxx number then I doubt if the Netgears default 192.168.0.1 will be on the same subnet as the cable modem.

How do I get the NEtgear and cable modem to talk to each other so that the laptop's DHCP will find the cable modem for the correct IP, subnet, gateway and DNS?

Thanks

Chris W · 04-02-2007, 00:33

Unless the router has an ethernet uplink port and the ability to completely disable the ADSL modem, it won't be possible to use it.

Your daughter will need a cable router, not an adsl one.

malice05 · 04-02-2007, 10:46

Hi,

The router has 4 Ethernet ports all with auto sensing an uplink port. I have used it in my home set up previously with another ADSL router modem (I have two ADSL lines at home) and I have successfully routed PC's connected to this DG834G to my other router for accessing the internet. DHCP on the other router worked fine through this router and PC's were auto configured for internet access through the first router. But as both routers were on the same subnet I think this is why it worked fine.

If there was some way to determine the ip range and subnet that the cable modem issues on its Ethernet port I could then configure the router to have a similar range and set up. But I cannot find how to do this. As I said in the first post, I am surprised that the cable modem issues an 82.XXX IP address to the laptop's DHCP when connected directly to the modem.

Any other suggestions? Thanks

MovedGoalPosts · 04-02-2007, 11:18

ADSL and Cable are different technologies. There is usually no way to connect the ADSL router to a cable modem, unless there is an ethernet based WAN port.

The LAN side of the ADSL router would work, but only to the extent of issuing the IP addresses to all the computers. The router would however not know how to send traffic to the internet, as there would be nothing connected on the LAN side.

The Cable modem is designed to communicate with one device only. Usually that is a computer, and therefore it will issue a single IP address. You can change the single device connected by powering off the modem, and connecting your new device. The router can replace a computer, and thus be the single device seen by the modem and yet provide your LAN services.

malice05 · 08-02-2007, 18:27

Both the cable modem and the ADSL router (to be used as a plain "hub") have Ethernet connections. NTL's support line had said it was possible to connect a wireless router to the cable modem, but I cannot see how to get it to work.

In order for the PC connected to the ADSL wireless router (hub) to access the cable modem for internet connection, the PC needs to be issued an IP and have the default gateway (and DNS?) specified as the cable modem's IP address which I presume is its LAN address. But the IP which can be seen
looks like a WAN address. Unless the cable modem can manage both a LAN and WAN IP I think the issuing of a LAN IP to a single computer is not going to help another device which routes traffic via the cable modem. I think!

Thanks for the reply though!