Most current Linux distributions do not use a DNS resolver cache in the same way that Windows and Mac OS X use.
These cases are likely outliers, as OS X 10.10.2 has resolved wi-fi difficulties for some users as well.
Nonetheless, we have received numerous reports about wi-fi issues appearing or persisting with OS X 10.10.2, and the large Apple thread on the topic continues to grow with user feedback about the same problem persisting.
However, a common DNS caching application sometimes used is the Name Service Caching Daemon (nscd).
It’s most likely not installed by default so there is no need to flush the cache.
Edit the 'MX Records to set the priority with higher numbers like 10, 20 and so on for the existing records.
You can delete these records at a later time after your changes have taken effect.
Thus, to clear DNS caches in OS X Yosemite 10.10.4, and 10.11 El Capitan, and presumably onward, the command string is as follows: That command flushes all DNS caches for OS X 10.10.4 .
Longtime Mac users may recall that command string is basically what worked in the release prior to Yosemite.
One persistent wi-fi complaint with OS X Yosemite, even after OS X 10.10.2 appears to be abnormally sluggish wireless networking performance and slow transfer speeds when Bluetooth is enabled concurrently with a wi-fi connection.
For users who experience the Bluetooth related Wi-FI issues, disabling Bluetooth will return wireless speeds to their expected rate, however, given that Bluetooth is required to use an Apple Wireless Keyboard, Magic Mouse, or Magic Trackpad, amongst other third party accessories, disabling Bluetooth is an unacceptable situation for many of these Mac users.
On a semi related note: I know this has been a touchy subject some places I have looked. For each DC, what should their local DNS settings be?