Q: Can't access Airport Extreme after Yosemite install.

The only thing I've noted now is that, as our laptop shares two users, we are able to connect to the USB attached drive if only one of us is logged in, but not if both of us are logged in. Whoever hits the drive first has ownership, and the second of us to login isn't given 'permission' to access the files.  I can say honestly that I tracked this previous to the Yosemite upgrade, but I can say for certain that in all the time we've shared use of our laptop previous to the upgrade, we weren't experiencing the access issue.

Owlmama, I'm on v7.6.4 of the Airport Utility, and IPv6 isn't enabled on either our laptop or our Airport Extreme.

That worked for me as well.  Thank you for the suggestion.   I read comments that some people do not get the same results, they should quit the airport utility and then reopen it and wait for a scan of airport devices.  You may alternatively try to open a Finder window and and see if the disk shows up under there.  Good luck. 

yes for me.  I hope it works for you as well.

Actually I take that back.  It worked at first but the second I turn the firewall back on then it dies off again.  Yosemite seems to have a bug with airport utility.  Not really pleasant. 

I had similar issues until I rebooted.

I have the same problem. Airport Utility will not find my airport extreme or my two airport express units. Clicking on network in the finder will not find my disks on the airport extreme. Turning off the firewall does nothing, rebooting does nothing, switching to the wired ethernet from the wireless does nothing. Manually mounting the disks by using command-k in the finder and supplying a URL for the airport extreme will find the drives. Manually entering an address for the airports in airport utility will bring up the units.

My guess is that bonjour is broken somehow, and in a way that only hurts a small subset of the Yosemite users.

Actual solutions from people who have had this exact problem (not something like it) solicited. Please note from the above that I have already tried rebooting, disabling the firewall, etc.

That is very unpleasant @ToToApp.  My AirPort Extreme is running version 7.7.3, I don't know if that makes a difference.  In Wireless Options under the Wireless tab I selected the channels to run on instead of using Automatic.  I hope this issue is resolved quickly for you.

Try the following - it is at least something that works for me every time...

About every time I launch Airport Utility, I get a green dot on the Internet globe. (I have working internet connection)

I see the Airport Extreme but its icon is gray. When I click on it, it states "reading settings on 'airport device name' but it will do that for a very long time.

And NEVER resolve the issue.

I have tried so many workarounds which are taking a very long time. The fastest one that works every time here is:

Go to the wifi icon in the menu bar and click on it and select "Turn WI-FI Off" - after that, click again turn it back on.

The Airport Extreme is Back online and ready for editing.

IHTH

Turning WiFi on and off does not work.

Okay, I HAVE A WORK AROUND. A real one.

The issue seems to be an issue with bonjour interacting badly with what seems to be a bug in the firewall code.

To work around:

Go to System Preferences >> Privacy & Security >> Firewall

Unlock the settings and go to Firewall Options

Set "discoveryd" to permit incoming connections.

Click OK.

REBOOT. It should not require a reboot to fix a firewall setting, that is a bug(!), but for some reason the change will not take unless you reboot.

(In fact, bonjour should work fine even without incoming connections being permitted to discoveryd. Something is buggy. I'm filing a bug report with Apple about it.)

Didn't have discoveryd on the list just iTunes, dropbox and wineskin, added airport utility just to see.

Airport Utility isn't the problem as it doesn't perform the bonjour protocol directly, it is a client of discoveryd. Adding it will not help.

As a diagnostic, try turning off the firewall and rebooting -- if the problem is then gone, the issue is indeed bonjour being blocked by the firewall. You probably should not run without the firewall long term but this will at least demonstrate what the issue is.

Same issue here. Running a second gen Airport Extreme on the latest firmware with a 2008 unibody Mac. I can connect to the HDD on the Airport Extreme after a reboot, but within five minutes it'll lose the connection again.

Well, I don't even have firewall turned on. It is set to off - for reasons as such.

So - this workaround is not applying to folks with FW off... Sadly ;-)