So, I have this strange problem…
Sometimes when I wake my MacBook Pro from sleep, it won’t re-connect to the WiFi. The WiFi symbol in the menu bar will stay grey.
I can’t even turn off WiFi via the context menu of that symbol. Also trying to manually connect with my WiFi does not work.
What works is: going to system preferences / network and turning off WiFi. This will, at first, cause the System Preferences to freeze. The window will remain in that state for about two minutes. After that time it will become responsive again and WiFi will be turned of.
At that point I can turn WiFi on again and it will connect with the WiFi instantly.
What also works is firing up a terminal and issuing the command „sudo mdnsresponder stop“. This command takes about two or three seconds to execute on my machine. After that short time, the MacBook will connect with my WiFi without any problems.
I have yet to figure out why this happens (and why my solution/work-around) works… any hints will be appreciated.
UPDATE: What I forgot to mention… when this strange behavior occurs, I can’t even start „Activity Monitor“ to kill mdnsresponder. The icon will just bounce up and down in the dock forever – meaning: until the problem solves itself or until I manually kill mdnsresponder from the terminal.
UPDATE2: The problem doesn’t seem to have much to do with mdnsresponder at all. I disabled TimeMachine three days ago and didn’t run into the problem described above ever since… If you’re having the problem, please try disabling TimeMachine and comment below if this measure resulted in a „fix“ for you, too…