Airport has a self assigned ip address and may not connect to the internet.

the solution might be to install the 10.5.7 combo updater (it has to be the combo updater version).

what happens is that the mac firewall blocks configd (which gets the ip address) and mDNSresponder due to some reason. you can see if you have this specific instance of the problem by "allowing all connections" in the firewall, and seeing if then you can get an ip address (temporary fix). if you open up the firewall log, you might see it blocking configd

if you do have this specific instance, then just install the 10.5.7 combo updater, which will re-verify configd and mDNSresponder.

but if allowing all in the firewall doesn't work, you might have another problem, just with the same symptom. search these discussion boards for similar topics.

Have you tried bypassing your router and connecting the ethernet cable directly from the cable modem to your mac? The symptom you are describing is what would happen if your router is intermittently acting flaky. You get a self-assigned IP address when your router for one reason or another is unable to issue an IP address.

Hi, I'm having a similar problem here. In the first few weeks of purchasing my MacBook, I could connect to the wireless network at home flawlessly. I take it to a friend's house and try connecting to a network there. I might have changed the settings, but I don't know what. When I take the MacBook back home and try to connect to the network at home, I get the dreaded "self assigned ip". I also have a iMac at home, and that connects to the internet with no problems. When the iMac and the MacBook are trying to use the same network, the MacBook always get the self assigned ip, while the iMac works normally. Before, the iMac and the MacBook could mutually use the network with no problems. Any help in sorting out this issue would be appreciated greatly.

I had this same sort of problem but with a cabled connection.....

(my solution may apply to a wireless network....)

The problem actually was my router failing but through some research I found out a little about self-assigned IP addresses.....

This may help - what it is doing is randomly selecting a IP number to use but this number probably doesn't coincide with anything which is why it can't hook up to the net....

What I did was record my IP address and then manually enter it in the field when in the Network window.....I also had to insert a router address (even at that stage I wasn't using one....) - this seemed to get the net up and running....

I have a Xbox360 in my network and it seems to fit into the network ok....

hope this helps or at least points u in the right direction

well have you seen if it's your firewall that's blocking you from getting an ip address? turn your firewall off and see if that works

This problem is widespread and I claim a solution (at least it worked for us). See my post here http://forums.macrumors.com/showthread.php?p=8087986#post8087986

Hey, sorry this is really late, the Apple Support page seemed to have gone nuts and wouldn't let me login. The problem has been fixed now, thanks very much for your help. If you have this problem, resetting the router seemed to have fixed the problem.