CloudFlare is a content delivery network and distributed domain name server service marketed as improving website performance and speed and providing security. Before one year i posted different methods to find out real I.P. behind cloudflare.
All those methods are only working , if there is admin misconfiguration.
I made simple bash script which do all things for you, you just have to provide name of website which is behind cloudflare.
chmod +x cloudflare-ip.sh
In script you have to change I.P. in line 45 . i used dns variable , because for unknown DNS my isp redirect to its address ,so we can know that response is valid or not.Change that I.P. according to your setting.