From time to time, when changing DNS configurations you will need to flush the local DNS cache on your computer. On a Mac, this can easily be done from the Terminal. Just run the following commands for your respective version of OS X…
El Capitan
sudo dscacheutil -flushcache;sudo killall -HUP mDNSResponder; say cache flushed
Yosemite (10.10)
sudo discoveryutil mdnsflushcache;sudo discoveryutil udnsflushcaches;say flushed
Mavericks (10.9)
dscacheutil -flushcache;sudo killall -HUP mDNSResponder
Mountain Lion (10.8) and Lion (10.7)
sudo killall -HUP mDNSResponder
Snow Leopard 10.6 and Leopard 10.5
dscacheutil -flushcache
Tiger (10.4) and Panther (10.3)
lookupd -flushcache