Cable modem default gateway problem

By Memorable_Fancy ยท 5 replies
Sep 15, 2007
  1. I've been searching for a couple of hours through the forums for a similar question that wouldn't necessitate making a new thread for something that's probably been asked a hundred times, but here's the haps.

    At home, I have my personal (very old) laptop which has all of my software, games etc. as well as a desktop that manages to be even slower than the laptop. The laptop is old to the point where the monitor is dead so I've got the desktop monitor and peripherals all running through the laptop instead. All of this isn't terribly pertinent, but I'll get to the significance.

    Today, we finally switched from dialup to cable internet. Since there's two computers but only one functioning monitor between them, there's no real reason to network the two, so only one computer will be hooked up to the cable modem at a time.

    ***The real problem starts here, so you can skip the intro if need-be***
    After some problems connecting with my laptop, I moved everything over to the desktop to confirm that the connection and the cable modem settings are all fine, but when hooked to the laptop, it gives a limited-or-no-connectivity error with the following details:

    Physical Address: 00-0D-xx-xx-xx-xx
    IP Address: 169.254.xx.xx
    Subnet Mask:
    Default Gateway:
    DNS Server:
    WINS Server:

    Since the connection works fine on the desktop, there's clearly some kind of error with my settings on the laptop. I've got slim to no experience with networking and broadband internet, though. Is there anything I can do to get this working?
  2. jobeard

    jobeard TS Ambassador Posts: 11,128   +982

    find the ethernet card and set the properties of DHCP for IP and DNS.
  3. Memorable_Fancy

    Memorable_Fancy TS Rookie Topic Starter

    Thanks for the quick reply!
    The TCP/IP protocol is set to get the IP and DNS addresses automatically, but it's still not connecting.
  4. jobeard

    jobeard TS Ambassador Posts: 11,128   +982

    please describe your ISP connection from the wall thru every box to your computer, each box connected, plus your ISP vendor.
  5. Memorable_Fancy

    Memorable_Fancy TS Rookie Topic Starter

    The ISP is Comcast. The connection is coming through a coaxial cable line, into an RCA DOCSIS 2 cable modem, through the ethernet-out line and then into the ethernet card of my laptop.

    The laptop is an old Dell Inspiron 5100 running Win XP home SP2.

    When setting up the connection, the same ethernet-out line from the cable modem was just pulled out of the laptop and put into the desktop's ethernet jack. The connection worked fine there, but gives the error message when hooked to the laptop instead.
  6. jobeard

    jobeard TS Ambassador Posts: 11,128   +982

    good description :)

    So one system works fine and the laptop fails -- clearly localized to the laptop settings.
    Start comparing the differences; most likely are the settings of the NIC cards
    OR the firewalls.

    The laptop is failing to get a reply for DHCP on port 67 while the other is succeeding.
    On the laptop, add a rule (specific syntax is dependent upon the software)
    which implements:
    allow tcp/udp in/out any-src any-dest port 67
    and move it to the TOP of the rule list (if you have that capability)
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