Ethernet connection to cable modem won't find proper IP Address

Just got a new cable modem, to which my 24" iMac is connected by a standard Cat5 cable. My ISP claims everything is right on their end, but no matter what they try, or how many resets of the modem I do, I get an IP address of 192.168.100.11, which is an address that apparently should only show up if I'm using a wireless network (due to the 192 starting numbers). Even odder, a router address is showing up even though I'm not using a router. That address is 192.168.100.1 (the only difference from the IP address is that it ends in .1 instead of .11). Equally odd, the IP and router address both disappear for no apparent reason, then appear again for no apparent reason. My ISP is clueless about how to solve this, and I'm lost at well. I'm hoping maybe some setting on my iMac can be changed to fix this. Any and all thoughts appreciated, as I'm currently stooping to borrowing my neighbor's wireless signal.

Thanks.

Mike

iMac 24", Mac OS X (10.5.1)

Posted on Dec 28, 2007 8:48 PM

20 replies

dechamp

Level 4

3,505 points

Jan 17, 2008 11:53 PM in response to mraibman

Sorry, in your last post you said you didn't loose your IP number from your router, just your connection. Now you say a Dell laptop also says it has a limited connection, which could mean the same thing. You can be getting a LAN IP number from the router, but the router doesn't have a WAN IP # so that's limited connectivity.

Since both machines lose the connection I don't think you can renew it by hitting the "button" in network prefs on the mac.

The router doesn't seem to be the problem, because you were having connectivity issues before you started using it. Everything points to the cable modem dropping the connection for some reason.

You never mentioned using two different computers on the connection before, so I assumed you wouldn't be running into a MAC number problem on the modem. That may be the problem, as your router does not have the same MAC number as the computer's ethernet card. The router usually has a setting where you can spoof the MAC setting for the computer into the router so that it identifies itself the same as the machine that used to connect to it. Not too many people have to actually spoof a MAC address anymore, so I'm not sure if that's it, or if the modem is just crapping out on you.

Now that you bring the Dell computer into the equation, and have added a router, and the nature of the problem has changed from a phantom IP number to a connection failure problem I would start with replacing the cable modem.

mraibman Author

Level 1

5 points

Jan 18, 2008 7:38 AM in response to imac007

Thank you both. Newest info:

Had the usual problem this morning. Went to Network Prefs and renewed the DHCP license. Suddenly, things were working again! (Whether this is a permanent way to avoid having to unplug, I don't know. But even if it is, I'd sure like to find a way to avoid having the problem in the first place.)

I also noticed that Airport had turned itself back on, probably when my wife last had to reset the system. I wonder whether that could be part of the problem? Although the ethernet connection was the primary, could the fact that aiport was connected to another network (my neighbor's) be causing some sort of confusion? (I don't know if this happens a lot, but I'll check the next time it wakes up to see if it's turning Airport back on even when we don't reset.)

As for the laptop, I should be clear -- it's my work computer, and I don't usually bring it home. So 99% of the time the wireless router is just shooting off a singal that no one is using (assuming no one has broken our password). the problem I am trying to resolve happens whether or not I have the laptop setup.

Thanks, as always, for any and all the thoughts.

Mike

mraibman Author

Level 1

5 points

Jan 18, 2008 9:21 AM in response to mraibman

Almost forgot -- I've had the same problem with two different cable modems (the other one was a Toshiba), so I don't think is the modem.

mraibman Author

Level 1

5 points

Jan 26, 2008 8:09 AM in response to mraibman

Problem solved. Firmware update to the wirless router did the trick. Yahoo!

mraibman Author

Level 1

5 points

Jan 26, 2008 8:09 AM in response to mraibman

Thanks everyone for trying to help! Turned out that updating the wireless router's firmware did the trick.

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Ethernet connection to cable modem won't find proper IP Address