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

What brand name is the modem?
The ip address is a standard local area network ip address.

Is your Airport wireless turned on? It may be getting an IP from a neighbor's wireless router.

What brand/model of modem are you using?

Your modem doesn't appear to be a NAT router, so the IP address and Gateway address in the 192 range shouldn't be happening (but you knew that).

So it appears you need to change something in the network to direct you to the problem. Can you borrow or have a friend bring over a WinXP machine? Arguing with an ISP tech support person is always easier when you put them in a Windows environment. Most of them can't get around the "Mac" issue and just blame Apple.

On the other hand, if the new machine doesn't have any problems with the modem, you might be able to isolate what's going wrong in your machine.

Mike,

This does NOT sound odd to me...

My DSL/router box is setup for 192. addresses and distributes IP addresses in that range...
It is not a wireless box...

If you turn OFF your Airport, then we can take the Airport out of the equation....

So, you are connected to your Cable box via Ethernet cable.
This box is giving you an IP address of 192.168.100.11
and the router (cable box) has an IP address of 192.168.100.1
I assume you have your Ethernet Networking preferences set for DHCP... Yes?

Can you browse the Internet with those settings above?
Do you also have a DNS number inserted in the DNS field that was given to you by your ISP ??

If you can't browse the Internet with the above settings, then of course something is wrong...
and most likely the settings in the cable box....

I would like to know more....

His modem is not a router and can only provide one IP number for one machine or to feed a NAT router. That IP number can not begin with 192.168 or 10.10 as those IP numbers are reserved for private LAN's behind a NAT router. That's why I assumed he was contacting a neighbors wireless router.

The manual for the modem shows examples of the number scheme that will show up in a Windows box. The numbers they show in the TCP settings in the Network control panel are typical of the WAN numbers that come into a router.

The manual does not show any method to access the modem by an IP number from a browser, so it can not be configured from the subscriber's end. Many Cable modems have done it this way for years. The modem is assigned to the user by serial number or MAC number and you have to have the cable company update their records before you can change to a new modem. It's a simple system, but also limited.

DSL service can also come with a plain modem, but you have to set up a "dial-up" account using PPPoE with your login and password. Fortunately, for me and my clients, the local Telco is Centurytel, and all of their modems they provide are either older Netopia or newer Westell modem/routers with a single ethernet port that can feed a hub for more machines.

Message was edited by: dechamp

He said it only happens with the Airport is OFF...

Therefore, if the Airport is OFF and the only thing plugged in is the Ethernet, then this IP address has to be coming from the cable box or ISP....
There is NO other explanation.....

I have seen many cable boxes, wired or wireless, that are routers....
I of course do NOT know the motorola box but many providers are now releasing new boxes with new software inside them....

If they can browse the Internet with the Ethernet cable and the Airport OFF, then the motorola box is working in my opinion....
Another way to check if it is a router is to connect the box to an Ethernet hub and then to a couple of computers... If the computers are assigned separate IP addresses, then the cable box IS a router.

The bottom line... If they can browse the Internet, then what is the problem????

I asked about the modem because I have a Motorola Surfboarder modem.
If I have problems connecting to the internet and unplug my modem and then restart it after a time, I still don't have internet.
If I unplug my modem and disconnect the ethernet cable and let the modem sit for 30 seconds or so, the plug in the modem and let it restart fully, then reconnect my ethernet cable, it works.
I had the same problem with a friend and we got it to work when we swapped the cable, end for end and in that case I dare say he wasn't getting a good connection as well.
As this is a new modem, it may still be the modem.
Just because it can establish a local area network does not mean it can link you to the wide area network (internet).
The computer is receiving a local area network address from the modem, which means the modem and computer are communicating, which suggests the ethernet cable is working as well (can still be a cable problem).

When you connect a different computer to a cable modem you must turn the cable modem off. You are paying for one IP address from the cable company. The cable modem memorizes the MAC address of the first computer to connect to it and will not let another computer connect. If you want to connect more than one computer to the cable modem at the same time you will have to install a router. The 192 IP address that you got is most likely the access to the service / statistics pages in the cable modem.

About that bottom line...

If a system, or piece of hardware works, you can blindly go about your business with no idea of how it works. This means you have no idea of why it quits working.

If you don't know how your equipment is supposed to work, how can you anticipate or troubleshoot any problems that may be related to the system you don't understand.

Most of the people in this boat just blame it on Leopard.

There are more explanations of why a computer will get a cached IP address. It's usually because it can't get another one and assumes an old setting that did work.

The guy said he was using his airport on a neighbor's router during the time he was having problems. The early messages he posted are not too clear on the exact state of connections when the 192 numbers appear or disappear, so it's hard to say what is going to happen/work, or when.

I did read the Motorola manual for his device, and it says it doesn't have a router function. His ISP agrees.

This thread has been running for a few days, with no feedback from the author, so further speculation if pointless until results from some of the suggestions are posted back.

A friend of mine is using a cable modem on Cox. He's been running into similar problems in that his router does work and he can see his other computers, but occasionally he has to reboot the cable modem to get back online.

Just about anything change in a DHCP network will wake up equipment and make it look for connections.

That solution came from Cox tech support, and I don't have any other information. Cable companies don't like to deal with router issues. Years ago, one of their techs told me that officially, they considered routers to be theft of service, and wanted me to buy more IP #'s and use a hub instead of a router. The growth of home routers has tempered their language a bit, but not their desire to support them.

Mac OS X 10.4 or later: How to change the MTU for troubleshooting purposes
http://docs.info.apple.com/article.html?artnum=303192

See if there is an MTU setting on the router.