I have this ongoing issue. If I run my Mac Pro for a few days all of a sudden the WiFi will disappear. Basically if I click the WiFi icon on the top menu bar it will show that the WiFi is turned on, but no networks can be found. However in Network preferences it will show that the WiFi has been turned off, and if I try to turn it on, it doesn't. If I restart the computer, the issue will go away. I don't need to reset anything, just a reboot will resolve the issue. It's not a network interference issue as I have the only 5GHz wireless AC network in my computer's reception vicinity and I don't have this issue on any of my other computers. When this happens, in console I get these messages: Code: 8/26/14 12:29:28.000 AM kernel: AirPort: Link Down on en2. Reason 2 (Previous authentication no longer valid). 8/26/14 12:29:28.000 AM kernel: en2::IO80211Interface::postMessage bssid changed 8/26/14 12:29:28.287 AM racoon: ioctl(SIOCGIFAFLAG_IN6) failed:Can't assign requested address 8/26/14 12:29:28.296 AM networkd: +[NETLedBelly stopFastFail] Clearing ledbelly failure cache 8/26/14 12:29:28.296 AM UserEventAgent: Captive: CNPluginHandler en2: Inactive I'm running Yosemite DP6. Any ideas? I'm thinking this is a hardware issue unless someone else things otherwise?