Cable modem and iMac don't like each other

in Genius Bar edited January 2014
They did like each other for a while. It worked, and it worked fine. It worked with the Linksys router connecting both my iMac 400 DVSE (9.1 and 10.0.x) and brother's Inspiron.

Then both of us couldn't get anything to come through.

After much hassle and both of us doing reinstalls and all kinds of kinky shit, nothing worked. I got the upgrade to 10.1 -- still didn't work. So, 9.1, 9.2, 10.0.x, 10.1, win2k all don't work.

Somehow, somewhere, somewhen my bro's Inspiron just starts working again. Sweet!

But mine still doesn't.

No idea why.

I've done all the regular restarting a billion times and using new cables and different ports on the router and hooking directly into the cable modem without a router and nothing seems to work.

Yes, I do have it on DHCP and through ethernet and all the preferences set as well as they were when the thing was working.

Anyone have any suggestions?

Is there an easy way to test the hardware to see if the ethernet port has gone bad?


  • Reply 1 of 13
    emaneman Posts: 7,204member
    Why don't you try calling up the cable company and see what they have to say. Whenever I have a problem with my Cable modem that's usually what I do first and things get cleared up.
  • Reply 2 of 13
    Which Linksys Router?

    Do you have the latest firmware?

    Cable company likely does not support multiple users behind NAT, so going to the will not be helpful.

    When you say it doesn't work what do you mean?

    Can you Ping the router?

    Can you connect to the Linky's web admin?

    Can you see the LAN?

    Are you getting one of those ghost IP addresses assigned? Sometimes problems with DHCP produce 69.x.x.x numbers. Only way I have found to clear them is to throw out the TCP/IP preferences...

    There's a great forum for Linksys support at

    Check it out if you don't get satisfaction here:

    <a href=",16"; target="_blank">,16</a>;

    Hope this helps.
  • Reply 3 of 13
    tltl Posts: 33member
    Well, being ass-early in the morning and me wanting to go to bed, I will give only one fact for clarification:

    The router is a 4 port with 4 columns of lights on the front. For whatever port my bro's computer is plugged into, the corresponding lights on the front light up. The lights don't turn on when I have my computer plugged into any of the ports.

    But I'm gonna be busy tomorrow all day so I won't have much of an opportunity to check out those other things.

    We spent weeks (months) calling the cable company talking and complaining and whining and wondering why the hell they weren't helping us, so I doubt they would be of any help.

    [ 11-29-2001: Message edited by: tl ]</p>
  • Reply 4 of 13
    Call your ISP to clear the MAC address.
  • Reply 5 of 13
    ac2cac2c Posts: 60member
    There is a possibility that the router is not recognizing the Mac. Check your net settings again and then ping to see just where the break occurs. If you don't get a ping to the router, then there is a router problem or a cable connection problem at the computer or router or a bad cable. Let us know what happens. (Also check if your brothers and your IP address are the same - if they are and the other computer is on, your computer will not work. If your router is accounting for a single IP address for the network this is not a problem. Try putting your IP address in as a static address and see if that works.)
  • Reply 6 of 13
    If your router isn't lighting up the port where your Mac is plugged-in, then the problem is between your Mac and the router, not outside. Even if the Mac isn't correctly configured to interface with your ISP, plugging the Mac into the router should light up the router port's light immediately (if the Mac is powered-on).

    Go into TCP/IP and Internet control panels and double & triple check all your settings. If they STILL look right, type your settings in here and maybe somebody else will see what's wrong.

    It could end up being something stupid like a bad cable, too. Try swapping ethernet cables with your bro.
  • Reply 7 of 13
    ferroferro Posts: 453member
    A cable modem was the best thing that ever happened to my iMacDVSE/iBook2... well except for 10.1......

    Whenever I have had troubles...

    And I have had troubles...

    It is usually one thing...

    Service - that either being unknown repair, upgrades, slowdowns or outages...

    Thats my experience anyway...

    Its never been as a result of anything I have done...

    Well sometimes I may confuse my browser by asking it to do too many things... at once...

    That sometimes screws up my cable modem...

    I dont know how thats screws up my cable modem...

    But after that I cant get anything to work... anything.

    I would usually have to either restart or do the "modem cycling" thing... I did find however that if you vigorously plug and unplug your ethernet cable...

    Sometimes it will work after that...



    [ 11-29-2001: Message edited by: FERRO ]</p>
  • Reply 8 of 13
    tltl Posts: 33member
    (I'm in 9.2 right now)

    TCP/IP control panel says:


    Connect Via: Ethernet

    Configure: Using DHCP Server

    IP Addy:



    Name Server Addy:


    all of which is completely bogus, because on the machine that does work IP=, Subnet=, Router=

    In the System Profiler, under Network Information:


    Ethernet built-in ........ Link: Down ........ Speed: n/a ........ Duplex: n/a

    Modem ........ Name:blahblahblah

    Open Transport ........ Installed: Yes ........ Active: Yes ........ Version: 2.7.8


    AppleTalk ........ Installed: Yes ........ Active: Yes ........ Version: 60

    File sharing: is off ........ This Network: 65280

    Default Appletalk zone: Not Available ........ This node: 128

    Active network port(s): Ethernet built-in ........ Hardware Address: 00.0a.

    ......................... Router: &lt;not available&gt;


    TCP/IP ........ Installed: yes ........ Active: Yes ....... Version: 2.7.8

    Pesonal Web Sharing: is off ........ USB Printer Sharing: Not Running(v1.0.2)

    Multihoming: is off

    Netmask: ........ Default Gateway address:

    IP address: ........ Domain: blank

    ............................. Name server address:


    if that's any help.

    [ 12-02-2001: Message edited by: tl ]</p>
  • Reply 9 of 13
    TL, I've been scratching my head over this one since you posted your configuration here. Doesn't make sense!

    In the TCP/IP control panel, are the netmask and IP addresses "greyed out" or are they "active" numbers, something you can edit or change?

    The thing that puzzles me is that since you don't have an ethernet link, there's no way a DHCP server could be setting the netmask and IP and router address for you. That makes me wonder where these numbers come from!
  • Reply 10 of 13
    More questions/suggestions:

    1. Is the PC that works on this router also set to use DHCP, or has the TCP/IP info been set manually?

    2. You say the settings on the PC that works on this router are IP=, Subnet=, Router= --- maybe you should try changing the TCP/IP settings on the Mac to "manual" instead of "use DHCP server" and manually select these exact same settings. You'll actually need to shut off the PC to avoid having two machines with the same IP address. If this works, then you can stick with manual TCP/IP settings, but choose a slightly different IP address (like x.x.x.101) that doesn't conflict with the PC.

    3. Have you double-checked the cable?
  • Reply 11 of 13
    Hi all

    I have the exact same problem as mentioned below by tl.

    My DHCP ip's addresses match with tl's exactly.

    The same cable when plugged into my PC works fine and i am able to get valid DHCP ip's.

    But as soon as i plug it into my PowerMac G4 AGP, i am unable to get DHCP IP's.

    Is there a solution for this ?



    [quote]Originally posted by tl:

    <strong>(I'm in 9.2 right now)

    TCP/IP control panel says:

    if that's any help.

    [ 12-02-2001: Message edited by: tl ]</strong><hr></blockquote>
  • Reply 12 of 13
    I have the same Linksys router, and I have never had any problems. Hmmm... You have a wierd problem, but I'll take a few shots in the dark.

    1. Make sure there isn't another DHCP server on the network or running on your computer.

    2. This may be a typo, but you should be on a 192.168.x.x network, not a 192.169.x.x network. 192.168.x.x addresses are specifically reserved for things like NAT. 192.169.x.x addresses aren't.

    3. Do you have VPC installed? I'm not a VPC user, but I use VMWare which is similar to VPC. VMWare messes with the network configuration in order to create a virtual node on the network.

    4. People often misdiagnose DNS problems as Internet connectivity problems. To avoid this, always ping ip addresses to test connectivity. Don't use a web broswer. From an OS X terminal, ping your router by running this from the Terminal: ping

    Then, if that works, test your Internet connection with: ping

    5. As others have pointed out, you could configure your TCP/IP manually rather than using DHCP. The following settings should work.

    IP Address:


    Subnet Mask:

    Domain Name Servers:,

    [ 02-23-2002: Message edited by: Brian J. ]</p>
  • Reply 13 of 13
    okay, a few things: first, i'm not really familiar with linksys routers, but do they run the NAT or is it on one of the copmuters (os x has a nat server you can use from the terminal, but if router does it, its not needed). whichever computer runs the NAT server (be it the mac, pc or router) should be setup to use DHCP.

    since u say the inspiron works, you can chk its ip (@ cmd line, write ipconfig), it'll probably be 192.168.x.y, and the mac should be y+1.

    The 169.z.x.y with messed up subnet is what the comp gives you when it can't hit the DHCP server. Behind a NAT, with a small number of computers, only the gateway needs DHCP. The comps can use the 192.168.x.y, where y differs for each, and their gateway, or router ip, should be 192.168.x.1.

    The way nat wrx is the gateway gets a real inet address from the dhcp, then fakes a few for teh inner comps. they each, within the little lan, refer to eachother with 192.168.x.y (actually in the lan, 192.168 can be anything, so long as x is constant, and y varies per comp), but to the outside, each of them is the same IP (=the "real"). the gateway then properly ROUTES the info to the proper end-computer.
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