HOW TO FIX : Airport has a self-assigned IP address.

HowTo fix: Airport has a self-assigned IP address and may not be able to connect to the internet.

By Philip Hoyos | in Apple

Sunday, May 9th, 2010

My girlfriend could not connect to our network, and Airport told her: Airport has a self-assigned IP address and may not be able to connect to the internet.

The problem was that her mac would self-assign a IP address, 169.x.x.x and Subnet Mask: 255.255.0.0. It seemed to be connected to our Time Capsule, though it did not get a IP address by the DHCP server. I tried renewing the DHCP but that did not work. I also tried accessing a ip address, as it could be an DNS error, this was not the case either.

Problem solving

I fixed the problem by manually setting up the network settings, to make sure they matched my own in, DNS Server, Router, Subnet Mask, and IP address +1. That worked but this could only be a temporarily solution as she uses her mac multiple places.

So I adventured out into the great indexed space of google to find a solution to the problem. As it turned out quite a few people was addressing the problem, and it seems to be a problem that Apple have had this problem for quite a while. In my search I found the problem has occured in an update to Apple OS X Leopard somewhere between update version 10.5.2 and 10.5.6. While the mac in question is at OS X 10.5.8 the problem still seems unsolved by Apple.

To fix the problem with Airport self-assigned IP it tried the following.

1. Booting into SAFE BOOT by restarting the mac and pressing the shift key.

2. In safe boot deleted the SystemConfiguration folder in this location:
Macintosh HD>Library> Preferences

This folder contains information from the System Preferences, and will be reconstructed if it is not found in the path. In my case it contains the following files, that I found should be deleted if I could not remove the entire folder:

• com.apple.airport.preferences.plist
• com.apple.network.identification.plist
• NetworkInterfaces.plist

3. I opened Keychain Access and found all the information about the network I was trying to access, and removed the login information by deleting the key. It appeared both in login and system. You can access Keychain Access, by opening Spotlight and type Keychain Access (this even works if your system is configured for another language than English).

4. Restarted the mac and voilár it worked…..but only shortly after a test restart the problem was back on again.

Solution

I finally found the solution which was very simple. The solution in this case was to:

1. Turn off Airport
2. Switch off the built-in firewall (found in: System Preferences>Security>Firewall), I set it to allow all incoming connections.
3. Turn Airport back on again….and it worked

I tested this solution to work, and it worked after a restart as well. I have no clue to what caused the problem, however, I hope that this information will be of value to others as well.

Tagged: Airport, IP, network, self-assigned

This entry was posted on Sunday, May 9th, 2010 at 22:40 and is filed under Apple. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.