wireless networking - Repurpose a cable modem/router as merely a router

07
2014-07
  • Zoë Clark

    Please bear with me - I'm unclear about much of the terminology used in home networking.

    The scenario:

    • I would like to set up a wireless network.

    • I live in a shared house where internet service is provided for free but the person in charge of its maintenance provides no technical support. In other words, all I have is a live LAN (correct terminology?) plate in my room. I do not have a working cable plate/outlet.

    • Left over from my last apartment I have a perfectly good Motorola SBG6580 cable modem/router.

    • I can connect to the internet using this configuration: wall plate<-- Cat 5 cable-->router/modem<-- Cat5 cable -->laptop. There are four unlabeled ports on the back of the modem/router so it seems to be acting as a switch (correct terminology?).

    • The cable modem/router appears in the list of nearby wireless networks and using the password on the bottom of the box I can connect to it and navigate the settings at 192.168.0.1 in my browser.

    • It seems like I have all the ingredients for a wireless network recipe, however, upon connecting to the wireless network, I cannot get online. My browser just tells me it cannot connect to the internet.

    This doesn't seem to be the typical "bridging" situation since I want to use the router I already have. And my situation isn't quite like this one since that OP has access to the cable for his cable modem/router. And I'm not sure if this is the same situation since the OP is using a DSL modem and isn't explicit (enough for my limited knowledge) about his configuration.

    Any ideas?

    • Answers
  • CharlesH

    first off your terminology was not too bad so not to worry :)...

    In my opinion you are correct that the router is working as a switch. You normally have four 'switch' ports on a router and an internet port which can be either for a phone line, Ethernet cable or coaxial cable depending on the router.

    Now what I believe is happening is that your DHCP 'Server' (basically gives network addresses to devices that request one) on the cable is coming from the main device (behind the wall socket). However when your connecting to Wireless your being given a new DHCP address which is then creating/putting you on separate network to the one your getting from the Ethernet Cable (so two different Local Area Networks).

    Various methods to getting around this however it all depends on how flexible that Motorola device is as I'm not overly familiar with it. BTW you have to be very careful plugging in devices to a working network as your device could conflict (DHCP) with the current device and stop everyone's access.

    Firstly I would start by logging on to that Motorola device and disabling DHCP completely on all networks. Then you can try to plug the device back in to the wall socket, log on via Wifi and see what address you get (possibly a 169.x.x.x which means no device is supplying an IP address). If that doesn't work you may have to look at static routes which tell the traffic coming from the wireless device where to be routed to get to the outside world.

    Have a look at turning off DHCP and let me know what changes.

    Thanks,

    Charles


    • Related Question

    Cable modem and router connectivity issues
  • Questioner

    So, I have a router that is plugged into my cable modem. I was getting connectivity issues, so I plugged my machine directly into the modem to find out which was the weak link. I could get connectivity plugged directly into the modem, so I figured it was the router. So, I bought a new router and I still have the same issue. Does anyone have any thoughts as to why I could get connectivity plugged directly into the modem, but not plugged into the router when it is plugged into the modem? Thanks.


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  • hyperslug

    Here are some guesses:

    • The cable modem is looking for your computer's MAC address only. The router needs to spoof that MAC.
    • The cable modem needs to be power cycled after the router is on and booted for the cable modem to connect.
    • The wireless network is not working, either on your computer or on your router.
    • The router is configured improperly for NAT.
    • One of the patch cables you are using is defective.
    • Both routers were defective from the factory.

    Try connecting modem -> router -> computer and logging into the router to see if it receives a WAN address from the modem. For example, a Linksys modem has a Status page that can indicate it is receiving a connection from the modem: http://ui.linksys.com/files/WRT54G/v8.2/8.2.05/StaRouter.htm