Comcast blocking Mac Addresses?

Discussion in 'Networking' started by unpossible, Dec 24, 2007.

  1. unpossible

    unpossible Member

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    Short version: Does Comcast block Mac Addresses?

    Long version: Yesterday, I thought my Comcast High Speed Internet connection went down. I thought at first it was Comcast having issues, but I first tried to rule out a problem on my end. I connected the cable modem directly to my computer (normally, the modem goes straight to a Linksys router), but still no connection. After calling tech support, as a last resort, she suggested I try plugging the modem in directly to another computer. I did, and much to my surprise it worked. She said most likely my router and/or first computer's NIC was bad. It wasn't very plausible to me, but I had no other explanation. I even switched back to the router, just to tell myself that it wasn't Comcast that was glitching and was just all of the sudden working, but I still could not get an internet connection.

    Several minutes later, I had a sudden realization. There was something that my router and my NIC had in common. I had the router spoof that NIC's Mac Address. So when I switched the router's spoofing to the second computer's MAC addy, voila, everything was working again.

    So again, the only possible explanation I have is that Comcast blocked the original MAC address I was using. So my question is, have Comcast been known to do that, and if so, why?
     
  2. Fardringle

    Fardringle Diamond Member

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    Yes, ISPs can and do block MAC addresses if they think there is a legitimate reason to do so.

    What have you been doing recently that is illegal or violates Comcast's terms of service? ;)
     
  3. bluestrobe

    bluestrobe Platinum Member

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    I know Cox.net will block MAC addresses if there is a known issue with that computer.
     
  4. w0ss

    w0ss Senior member

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    I haven't had comcast in probaly three years. But I do remember they did block my mac address at least twice. They always gave me no reason as to why, and unblocked it as soon as I called. I figured it out the same way as you. The easy way to fix it is just change your mac.
     
  5. fleabag

    fleabag Banned

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    If they block your router, you can always "clone" a mac address from a working NIC onto the router to make it work.
     
  6. TC10284

    TC10284 Senior member

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    Or make one up. But I don't know if that's the legitimate way or not...