Changed my MAC Address with a program called Macshift and then I could not connect to the Internet using Comcast Cable?

Posted on 2006-03-29
Last Modified: 2012-08-14
I changed my MAC Address with a program called Macshift and then I could not connect to the Internet using Comcast Cable?  Can I get reconnected to the internet through Comcast Cable after changing my MAC Address with MacShift?  Could I use the Comcast Cable Self Install Kit to get reconnected after changing the MAC Address?

Question by:gdkinney_2
    LVL 95

    Accepted Solution

    Turn off the cable modem for 1 minute (unplug it).  Then reconnect it.  Cable modems don't take kindly to changes of Mac Address without a reboot.
    LVL 3

    Assisted Solution

    Not sure about comcast but most cable providers use your mac as a means to authenicate on there network. So you changed the mac address of your broadband modem? If so you will have to call Comcast to hav them register  the new mac address on there side
    LVL 3

    Assisted Solution

    Comcast (like many other ISPs) lets you access the internet with a specific MAC address.  Once this address is registered in their DHCP server, it will refuse to give you another address (as it is expecting to see your old computer again).  Just call Comcast support and tell them that you switched PC's.  They'll remove the old MAC address from their records and when you reboot everything the new one will be registered with them.

    Of course, the alternative to this would be to change back to your old MAC address (because it really shouldn't be necessary to change yours in the first place).  Also, if you are using a router with the Comcast service, you should have the router's external MAC address imitate the one of your originally registered computer.  This will allow you to continually change the computers connected to the internet (through the router) without Comcast ever knowing and cutting you off because of it.
    LVL 15

    Assisted Solution

    Not to mention that Comcast might not take kindly to it either. They may view that as you trying to find a valid lease to establish a freebie connection. Use caution or change that MAC address back if possible. In the original paperwork when they installed your cable modem, they most likely have a sticker on that sheet that shows your MAC address.
    LVL 5

    Assisted Solution

    I used to have comcast (I have cox now that I've moved) but they don't use your PC's mac to authenticate to the UBR, they use the cable modem's Coax interface MAC address.  That's the only one they actually "register".

    The problem is likely with the modem.  When the model is provisioned for 1 computer connection, it won't offer IP's or talk to any others.  You need to make the modem forget about your MAC address.  The easiest way is to unplug it for a few seconds, but if that doesn't work, navigate to its config page (usually at and find the button/link for factory reset.  That'll do it.

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