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Comcast DHCP question

Discussion in 'Networking Issues' started by RodFather, Mar 9, 2005.

  1. RodFather

    RodFather Guest

    Hello all yea am a newbie with a question but I promise to stay active. My questions is this, what is the best way to force a WAN IP change with Comcast DHCP.
  2. neoufo51

    neoufo51 Network Guru Member

    I would also like to know how to change my IP using comcast and a linksys router.
  3. bluebox

    bluebox Network Guru Member

    You want to force the Comcast network to reassign you a new IP on demand? I don't think that can be done. Besides wondering to myself why you would want to do that anyway, the comcast router would only assign a new IP if you were

    a) A new client joining the network
    b) At preset intervals

    Since the network always knows what client is what sunscriber, you can't trick it into reassigning an address just by changing MAC address or whatever. (although it could work depending on the equipment configuration on your node I suppose...)

    So, unless I'm missing something, I don't think you can do it.

    Why don't you tell us why you want to do it, there may be a better way to skin this cat.
  4. tekuru

    tekuru Guest

    Actually, an easy way to force an IP change on a comcast cable modem (I am in Connecticut), just change the WAN MAC address. After doing this and letting the router apply the settings, you will need to power cycle the cable modem, and then either release/renew the routers WAN IP or just power cycle the router, too. (which essentially accomplishes the same thing).

    I originally noticed this when replacing a router, I assumed I would get the same IP (since it was the cable modems MAC address I had to register when I signed up for service) however it seems that the router/nic's WAN is passed through.

    Another thing I tested was changing the new routers MAC to be the same as the old one, and I was given my old IP address back. This worked for a couple days, then I just stopped trying. I don't know how long the DHCP lease is from comcast.

    Just remember to reset the cable modem after changing the MAC on the router, you won't get an IP address if you don't.

    Nor'Easter 2006 - 500 Man LAN - http://noreaster.lpane.net

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