Airport can't get proper IP address.

There are a few posts about this issue and there doesn't seem to be a consistent solution posted on these boards. I can tell you that I had this issue and searched around for answers. Many suggest creating a new location and deleting the SystemConfiguration folder located in /Library/Preferences/SystemConfiguration, and then restarting.

Creating a new location did not work for me. Nor do I recommend deleting the SystemConfiguration folder as afterward my MiniBatteryLogger app would keep crashing, even after I deleted it along with all related files and then reinstalled. So there's stuff in that folder that is essential for the proper functioning of apps and the like, so I wouldn't mess with it. (Luckily I had a backup of the SystemConfiguration folder and when I restored it, everything worked again.)

I can tell you that I did get this problem solved by logging into a different user account which for some reason, connected just fine. Then I logged out of that user and back into the original one and everything worked. Why? I do not know. But I was happy to see the airport icon appear normally without the blasted exclamation point showing...

See if it works for you. I'm curious.

Sorry to hear that. I had that same frustrating angle to it; when plugged in via ethernet it would generate a good IP address and the wireless appeared fine too. The moment I would unplug the airport menu bar icon would suddenly have the exclamation point appear.

The thing is I know there is a fix. I had this happen on my wife's machine that I brought into work to send off for repair. I booted up in the office and had the 'self-assigned IP address' dilemma. I sent it in for repair and when I got it back, a few System Preferences were changed and the problem was gone. I never mentioned it to them, the repair was to replace the top case.

I called them and tried to find out what they did but they couldn't or wouldn't tell me.

Good luck. I hope this problem gets figured out soon with an update or something. It seems fairly widespread.

I had this exact same problem last night. I brought my new MacBook Pro home a few days ago and had been connecting to the main wireless network in the house without problem, then suddenly last night the connection failed. I repeatedly got messages about Airport's IP address not being able to connect to the internet, etc. The iMac that shares its Internet access was working fine and had internet. My iBook G4 was able to connect wirelessly on the network.
After an hour or so of trying to fiddle with settings, locations and such on the MBP, I went over to iMac that acts as the base station and simply reset the internet sharing setting in system preferences. The problem was solved immediately. Go figure!

I had used Ethernet to connect my two laptops during the day; maybe that had something to do with it...but the Airport failure happened several hours after I unplugged the Ethernet cable (was able to connect wirelessly in the interim).

I think I have tried every suggestion posted on the Apple Discussion Boards and still the Exclamation Mark shows, and I have no wireless connection. I am going to see an Apple Genius this afternoon and will post the solution when I return.

Ok I went to the Apple Genius Bar and booted up by Firewire with the Genius Drive, all of my hardware worked. When we tried booting from the hard drive I was unable to connect either by ethernet or Airport. The ip's were self-assigned and the Wireless indicator was marked by an exclamation point on the menu bar. I should mention that my ethernet worked fine connected to my home network but could not get an Internet connection (this should have been a big clue).

Although I had already re-installed Snow Leopard (and combo 10.6.2), the Genius was worried that not all of the files were re-installed because I did not do a clean install. So I went home and booted off of my Snow Leopard Install Disk, erased my MBP hard drive and reinstalled SL.

Internet connection worked fine until I installed the combo update. Then the same problem developed. Frustrated I again searched the Internet for any clues and I ran across an interesting solution focusing on the SL firewall. http://forums.macrumors.com/showthread.php?t=384947&page=5

It instructed to use Terminal to flush ipfw cache. I am not a Terminal or Unix expert in any way but since I am always backed up I wasn't really concerned. So I tried it and it worked! But be careful as Terminal commands are not for the faint of heart and I was desperate.

I do not want to be without a firewall so instead of using the SL user interface, am trying Door Stop X on a trial basis. At first when I turned it on I again ran into problems, but after some research I configured it to allow an Internet connection.

I am not sure why the SL firewall overtime shut me down because I did not change anything (although I understand some software brings along its own firewall changes). It is all working fine now.

Message was edited by: Robert Deleeuw

Message was edited by: Robert Deleeuw

Message was edited by: Robert Deleeuw

Wow I did quite a bit of searching when I had the problem. Wish I found that solution before I went ahead and re-installed everything...which seemed to fix the problem.

If it comes back, I'm going to try the Terminal command solution for sure.

Well just be careful as I am not an expert!!!!! I was just out of ideas and was ready to try anything.

BTW to all the experts, if anything I posted is bad advice please tell me and I will remove it.

Trust me, anytime I mess around in Terminal I know I'm taking my own destiny into my own hands. I keep a clone of my computer handy just for such a situation in case I have to go back to how things were.

Anyway, thanks for sharing. This problem is extremely frustrating and somewhat widespread, at least as far as problems in the world of mac's go. So any other things worth trying are worth sharing.

Your problem at your friend's appears different and could have been caused by the type of security the Verizon router was using (WEP vs WPA2) which happened in Leopard to me. My problem turned out to be a subtle firewall problem that I could not fix thru the normal UI. I was desperate to get it fixed and only cleared out the ipfw cache thru Terminal after the Apple Genius Bar and re-installing the SL system did nothing.

I only use Terminal if I don't have alternative ways of addressing the problem. And did not advocate its use here.

Message was edited by: Robert Deleeuw

Message was edited by: Robert Deleeuw

We have 2 identical computers (one black on white) running the same operating system (Snow Leopard) using the same network a (Deutsche Telekom wifi device). One computer connects perfectly to the net without problem, the other gets an airport self assigned IP address and there is nothing that can make him change his mind! This is driving me crazy! I even tried to put the ip address manuaually. Then, the airport sing in network preferences turns green and says everything is fine but it still does not connect to the internet!

I tried everything in the forum, including flushing the IP addresses. Nothing seems to make this computer get an IP address from the router. But with other networks, the computer works fine! Is there any other trick I can try? Thanks!

Nikolas