Flush DNS cache

Windows

ipconfig /flushdns

Macintosh OS X

sudo dscacheutil -flushcache 
sudo killall -HUP mDNSResponder

Linux (depend on distribution)

/etc/rc.d/init.d/nscd restart 
/etc/init.d/nscd restart
/etc/init.d/dnsmasq restart
/etc/init.d/named restart