New MBP ethernet/DHCP does not work plugged directly into cable box, old one did?

Discussion in 'Mac Basics and Help' started by 73CortinaV8, Dec 16, 2011.

  1. 73CortinaV8 macrumors 6502

    Sep 4, 2006
    Palo Alto, CA
    I bought my elderly mother a new macbook pro 13 to replace her dying ibook G4.

    Apparently (I'm helping her from 3000 miles away), her old ibook was plugged directly into the ethernet out on her cable tv box.

    And this worked fine. Network was setup for DHCP. It would get an address and there would be internet access.

    But if she plugs her new MBP into the same ethernet port, she gets no DHCP assigned address (just a random one that happens when there is no DHCP), no router, no DNS. The status of the ethernet in the networking preferences is green though, it says connected. But DHCP does not seem to work.

    I had her compare the settings side-by-side between the two computers, and they are the same.

    Anyone have any ideas on this? Are cable boxes someone programmed to only recognize a certain MAC address? Seems unlikely.
  2. squeakr macrumors 68000


    Apr 22, 2010
    Did she try power cycling the modem to reset it?? Sometimes this helps. I know that in the past certain providers would only allow the first MAC address they saw on the system as an authorized computer (this was to keep people fro running networks on their system as they charged more for networks than the casual user). The work around was to clone a mac address into your router to fool the system into thinking only one system was connected. Power cycling the modem can reset the MAC address lock if that is the case. Are NAT settings configured the same as well. I would tell her to power down for about 30 seconds-1 minute to clear the cache and then power up and reconnect the new system.
  3. aristobrat macrumors G5

    Oct 14, 2005
    x2 on the cable modem power cycle. Mine doesn't seem to recognize that devices have changed until after a power cycle.
  4. 73CortinaV8 thread starter macrumors 6502

    Sep 4, 2006
    Palo Alto, CA
    thanks. I did have her power cycle it, but just for 5 seconds. I'll try a longer power cycle and maybe I'll try to have her clone the MAC address of her old laptop to the new one.
  5. samh macrumors 6502

    Oct 29, 2009
    Rather than clone the address, she could also try calling the ISP. If it's a MAC address issue they can reprovision.

    They may also be able to identify what the problem is, if it's not a MAC provisioning issue.

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