Q: Self assigned IP address

Are there any other devices on the same network, and are they able to get an address?

Try a wired connection, if that's an option. If you can connect wired, but not wirelessly, then the following support articles may help:

Joining an encrypted WEP or WPA Wi-Fi network

Troubleshooting Wi-Fi issues

I had this happen to me twice and the solution for me was to delete the wifi network and keychain password.

The first time i fixed it by restoring from Time Machine which took a long time. I also tried the renew DHCP, delete com.alf.plist etc to no avail.  The second time I found a better solution from someone on this forum:

Go to Network Settings

Turn Airport Off

Click Advanced tab

Select my wifi network and hit minus sign to delete

Click Okay

Click apply

Go to Keychain access in Applications/Utilities

Find your network name in the list and delete that password login

Then go back to Network settings and turn airport back on

Click Advanced

Click plus sign then Show Networks

Choose your network and re-enter your password

Click Okay

Click Apply

Then airport should work again, this is what fixed it for me.

All the best

Thank you, a simple and excellent answer which helped me greatly!

Excellent solution. Thank you!

It helped me after a day of frustration: my mac would not connect to home wi-fi network at all but would to everything else.

One of the clues should have been the keychain password entry for the network as it was much longer and incorrect, compared to another mac's keychain entry which was connected to the same network. As soon as I saw your instructions I felt relief.

Totally worked - definately some sort of key chain conflict!!

Thank you so much! solved my problem so simply.

I know you seem to have got things sorted, but for others for whom this may not have worked, here is how I got over the "self-assigned IP" problem

system preferences>network>

with airport selected, go to "advanced" and then select TCP/IP

In the "DHCP Client ID" box (which is usually empty) put any random string of numbers

THEN renew the DNCP Lease,

It worked for me after trying a lot of other ways

PL

I've been searching forums for 3 days now and none of the 101 things I tried have worked until this.

THANK YOU THANK YOU THANK YOU!

Glad to be of help.  I cannot claim credit but unfortunately have lost the original source for this (another, non-apple forum).  It really is strange how many "final solutions" there are for this problem, that don't actually work in all cases.

Anyway - spread the word - maybe YOU can help someone get over this annoying problem

PL

Came home today and my wifi wasnt working again, tried the "random string of numbers" trick again but it didn't work this time. BUMMER. Guess it wasn't a permanent fix... any other ideas?

So sorry to hear that.  The only other trick I have is the following.  I don't know if it will help for you

Applying a manual IP under the Configure IPv4 selection should work.  In your home router this will be 192.168.1.X .  However, this for me is not where the problem lies - for me it is when out on the road using a third party WiFi, what IP to use?

You may find that your iPhone can pick up the network.  If so, check your phone under settings / WiFi right arrow on chosen network and see what IP your phone has picked up.  Put the same IP into your laptop using "Manually" - just use a different last digit

That the extent of my suggestions I am afraid!

PL