After some research and experimentation, I have found that the easiest way to reset the DNS cache on an Apple iOS Device such as an iPhone is to switch WiFi off and on. This works everytime for me.
Just a quick post if only to make a note of this for myself. For years the method of clearing the DNS cache on a Mac has been
This command runs OK on OSX 10.8+ but doesn’t actually seem to clear the DNS cache. On OSX 10.8+ the command you need is:
sudo killall -HUP mDNSResponder