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Comcast not working with my iMac G5

Discussion in 'Macintosh Computers' started by Candyfingered, Mar 17, 2005.

  1. macrumors member

    Anyone else encounter and issue when plugging a comcast cable modem into a Mac where the Mac just doesn't read the modem? I can't get the iMac to identify the IP address using DHCP and everything set up as it should. I've read other have had this issue but as yet have found no solution. The Mac just doesn't read the modem (though my old PIII Windoze laptop does)
  2. macrumors 68040


    Does the modem's "PC" light come on when plugged into your imac?
  3. macrumors 6502a


    You're not using one of those USB modems are you?
  4. macrumors member

    Not sure. I'd have to check when I get home. Is that one angle to take? That comcast isnt' recognizing the Mac as a computer?
  5. macrumors member

    No, Comcast cable modem connected to the iMac directly with a CAT-5 cable.
  6. Moderator


    Staff Member

    Is it also a router? Do you need to configure it to dispense IPs?

  7. macrumors 68000


    Comcast has been known to keep MAC addresses on file for the computers that are using their modems. If the MAC address doesn't match the one on file (which might be your PIII computers MAC address), they wont let you get on. I suggest unpluging the power cable to the modem, and let it sit for a couple of minutes before plugging it back in and seeing if it works. After that, I suggest calling up Comcast, and telling them that you have a new computer that you want to use to replace the old one. They will go though the steps of changing the computer and should hopefully solve the issue if unplugging and plugging in the modem didn't work.
  8. macrumors 6502a


    As long as you've got your TCP/IP set to use DHCP I don't know what else needs to be done... Do you have to activate your account or something of that nature? Read the manual yet?
  9. macrumors member

    No the account has been active for 6 years. Unless Comcast decided to deactivate it in the time between when we unplugged one computer and plugged in the Mac then no that's not the issue.
  10. macrumors 603


    I second this suggestion, and suggest that you try resetting your modem (if you haven't already) by leaving it unplugged for some amount of time. Plug it back in and restart your mac.
  11. macrumors newbie

    I had a problem connecting someone's Mac on Comcast last week. The Mac was getting a valid IP address from DHCP, but it was not getting any addresses for DNS servers.

    I called Comcast, and they insisted that the DNS addresses would be filled in automatically. I asked them for the addresses of the DNS servers and they refused to provide them, claiming that the addresses of DNS servers change all the time (which I doubt).

    I Googled around and found some old Comcast DNS server IP addresses, entered them into the Network preferences, and that fixed the problem.
  12. macrumors 601

    Since reading this statement, I think your problem is that the modem still has the other computer's information on the "lease". You need to release the IP address get a new one. It's easy. Turn off your modem for about 30 seconds, plug in your iMac. Turn on the modem.

    This should work. You'll need to do this every time you switch computers. If you plan on doing this a lot, just get a router.

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