Help Please! 169 self assigned IP address trouble

Imac/Shaw Cable/169 IP address

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Ok, this has been going on for four months now, I have had help from all directions, to no avail. My IMac (Tiger 10.4.11) is kicking out a self-assigned 169 IP address with all Shaw cable modems I have tried. No network, no router. It works fine at other locations and with ADSL modems. My brothers PC and roommates Mac book both work fine.

I have erased and re-installed and upgraded my OS, to no avail. I have traded out all cables and had Shaw service calls. I have taken my comp to a Mac service center and he could find nothing wrong with it.

For a while, after the modem power cycled it would kick out a 192 IP address for a couple minutes then revert back to the 169.

Airport/bluetooth are disabled, built in ethernet is the only configuration selected and everything is set to automatic

Apple help was unable to figure out the problem with phone techs basically asking me to let them know if I figure it out because they don't have a solution.

Please can anyone help? I am getting frustrated with my very expensive paper weight so suggesstions and info of any kind are welcome.

First things first. Are you trying to connect with PPPoE or DCHP?

You should be connecting using PPPoE and providing the username/password in your network settings. Ideally, you'd have a router do this for every machine in the house. If the cable modem is acting as both a modem and a router for other machines (you mentioned other machines are connecting but don't say how) then this might be a problem.

I actually had my airport express connected to my cable modem for 8 months using DCHP and had all kinds of issues that went away when I set up a PPPoE connection like I should have from day one.

Hey, sorry yes its DHCP. The other computers I referred to were able to connect through this modem when tested. There is no wireless routing in the house.

For some reason all Shaw phone techs have told me I can only use DHCP, it has worked in the past, just quit on its own one day.

For three years I never had a problem with this set up.

OK, well that's strange. Does the iMac work with other ethernet connections? If it suddenly stopped working then something must have changed?

I know, thats what I thought and why I did an erase and re-install of Tiger. I connected to my roommates laptop via the ethernet port with no problem. I also connected to a friends ethernet and was able to download all software upgrades for OS X, Safari etc . . .

Really kind of at a standstill . . .

What happens if you record the IP and DNS information that is given to one of the other computers, the manually plug that information in.... I would try to see if you could static the information first and then go from there.

Another idea is to delete the adapter from the list and let the system create a new one. It could be corrupt for some reason.

gave it a shot. it said I was connected to the internet via built-in ethernet and the ip address I typed in but still couldn't get anything from the ISP.

Which adapter list are you referring to?

Cheers

System Preference / Network

In there is a list of network "connections". Below the list is a + and - sign. Highlight the Airport connection and click the - sign. Then click the plus sign and setup a new Airport connection to the TC. This will clear out all of the settings and start you fresh.

crap, no dice. I deselected every connection and then hit apply. Then re-selected built-in-ethernet-only and hit apply. I am not using airport so it shouldn't be selected as an active connection right?

there must be a way to stop this thing from self-assigning its own IP address. Some setting, somewhere.

Thanks

If the cable is plugged in it is Ethernet if it isn't it is Airport. I assumed that you were working with the Airport connection which is why I had you remove that one.

The self assigning IP is due to the failure of it getting an address from the DHCP server. There is a request and acknowledgment that happens between your computer and the DHCP server that is the router. For some reason your computer is not accepting the information where the other computers are. You are certain that under the connection that you are using that DHCP is selected?

yes, under the automatic location, built-in ethernet is the only connection selected. In there TCP/IP settings, configure IPv4 is set to Using DHCP. I switched it to manual and plugged in the IP address from this computer but received nothing from the ISP, even though network status said I was connected to the internet using that manual address. Earlier on I'd get a 192 address and when I hit renew DHCP lease it kicks out the 169.

I'm not sure at this point... If it were me I would probably try to just reload the system because something isn't right.

Thanks for the effort

I wold love to hear from anyone else. I know there is a solution out there . . .

As described - you are not getting a dhcp lease - so the mac just self assigns. Sometimes cable modems are assigned MAC (media access control) addresses - but since you are plugging in (I assume) random machines and they just work I doubt this is the problem.

Open console - and watch the system logs when you connect - does it say anything?

Another thing to try - since it works with other machines - is put a home router in (borrow one from a friend) - and let it connect to dhcp - if that works - let it serve dhcp internally and see if your mac can get a lease from the router.