Thanks for the info
I couldn't find anything about the "Scientific Atlanta DPC2100R2" specifically but Scientific were bought by Cisco a few years ago; I think this
is the specification (it's for the Cisco Model DPC2100 DOCSIS 2.0 Cable Modem - 7007012H) and this
is the user guide (it's for WebSTARTM Model DPC 2100TM and EPC2100TM Cable Modems). Both took lot of finding -- Cisco is one of those companies where the marketing people dominate over the technical
Based on those documents, the DPC2100R2 is meant to be used in a very simple way; the user configures their computer(s) for automatic networking configuration and it "just works". I assume that's how it is for you now -- any computer configured for automatic networking configuration can be plugged into the DPC2100R2 and is able to connect to the Internet.
Under the hood this is using Dynamic Host Configuration Protocol (DHCP)
to configure your computer with IP address, netmask, default gateway and DNS servers -- the essentials -- with values given out by the DPC2100R2. For Linux systems it helps to know that.
Back to the Belkin. It seems that it has got into a "funny" state. Assuming that it is not actually broken it should be recoverable by resetting it and then reconfiguring it following procedures in its User Manual.
First, the reset procedure. Follow the procedure on page 6, paying particular attention to the Power/Ready light to see if it behaves as expected.
Now for the re-configuration. I presume you want to configure the Belkin as a Wireless Access Point, that is you will wire it to the DPC2100R2 and then connect all the other computers to the Belkin by wireless and thus
- to the Internet via the DPC2100R2.
- to each other via the Belkin.
Follow the procedure on page 8. In step 1.2 you will be connecting whichever computer you are going to configure the Belkin from directly to the Belkin -- AFAIK you do not have a router, or an Ethernet switch-or-hub.
Presuming you do not have a Windows computer, you cannot follow the procedure in sections 2 and 3 so skip to "Using the Web-Based Advanced User Interface" on page 14. We are going to do the Ubuntu Karmic equivalent of what it says there.
During the reset, the Belkin set its IP address and netmask to 192.168.2.254 and 255.255.255.0. For a computer to connect with it, the computer must be in the same network range. We are going to use 192.168.2.200 and 255.255.255.0. This is known as a "static" address because it is fixed, unlike when getting the address by Dynamic
Host Configuration Protocol (DHCP) when the computer may get a different address each time.
Unfortunately I don't have Ubuntu. I tried to find a web page showing how to do this using GUI tools (Network Manager?) but found only pages saying Network Manager is broken and the best thing to do is remove it! That's what I did when running ubuntu Hardy. Seems like you have to use the command line to edit the /etc/interfaces file and then restart networking. Procedures here
- Make a backup copy of your existing interfaces file!!! You will want to restore it after configuring the Belkin. Something like this
sudo cp -p interfaces interfaces.bak
- The second procedure suggests removing network-manager. I don't think that is necessary.
- The procedures suggest using vi, nano or kate to edit the file. If you are not comfortable using any of them, post back for a workaround.
- Use these settings instead of the ones in the procedures:
Ensure that your settings have worked by using the ifconfig command and inspect the values for eth0.
Now continue with "Logging into the WURE" on page 15.
I don't know much about wireless so can't help much from here on. On page 22, I think you want "Wireless Access Point" mode. Hopefully that will make the Belkin transparent and computers attached by wireless will be able to get their network settings from the DPC2100R2 by DHCP. Once you have the Belkin working as you want, it's useful to save the configuration as explained on page 35.
When you have finished setting up the Belkin, copy the /etc/interfaces file in case you ever need to use it again and restore the old one, something like this (assuming your original interfaces file was backed up as interfaces.bak). This has not been tested
sudo cp -p interfaces interfaces.belkin.G-F5D7230-4
sudo cp -p interfaces.bak interfaces