How to get all IP addresses of a domain?
Need this data to create a special rule, and I need to know if they change frequently or not. Somebody told me that they have a dedicated IP range on Akamai.
There is no reasonable way you're going to be able to block facebook (or any other large website for that matter) purely at the IP level. You're going to be constantly adding and removing IPs, likely on a daily basis.
This is the job for a proxy, where you can properly block sites at the URL level and not have to worry about what IP addresses are behind them.
If you want to block facebook do it at the DNS level or use a web proxy to filter the content.