How I fixed my broken wifi after the Mac OS X 10.6.4 update


Yesterday I grudgingly let Software Update reboot my computer to install Mac OS 10.6.4. After it booted up, the wifi was dead.

Now my first thought the router wasn’t working, but my iPhone and my other laptop were still connecting just fine.

I looked in the network settings and found the IP address was invalid. It appeared to be a global network address, not a 192.168.0.* address for my internal network. How puzzling.

After some Googling around, I found several “fixes” which did nothing, including holding down Option-Command-P-R while the system boots to clear the configuration, deleting a network config file, removing and re-adding the Airport connection… nothing. Just a waste of time.

Finally I figured out a working solution on my own. The problem turned out to be DHCP. See, normally DHCP is the protocol that assigns an IP address to your computer. Without it, you’d have to enter the address manually.

Here’s what I did:

  1. From the wifi icon, at the top of the screen, select “Open Network Preferences.”
  2. Select Airport from the list and click the Advanced button.
  3. Select the TCP/IP tab
  4. In the “Configure IPv4” drop-down, select “Using DHCP with manual address”
  5. The “IPv4 address” box becomes available. Here’s where you enter an address. (See below)
  6. Disable Airport, then turn it back on.

If you’re wondering, the IP address you enter will depend on your configuration. I entered and there’s a good chance that if you have fewer than 7 other computers on your network, that will work for you as well. This part may take some experimenting and knowledge of your router’s typical assigned IP addresses.