Alrighty! Buckle, I am gonna make this sharp, concise and to-the-point!
Open you cmd.exe.
type --> nslookup facebook.com, below is the output
ok so let me explain the above stuff to you guys. Non-Authoritative answer means - I don't have any specific DNS server configured in my windows machine so my request was sent to the free DNS available on the internet. The answer is there but it's the best effort. The addresses 2a03:2880:2110:df07:face:b00c:0:1 is the IPV6 address for the Facebook, however we are not interested in that we are looking for the IPV4 address. And there it is, 126.96.36.199.
Copy this IP address and jump into Whois.net and copy this over there in the search box. You will find something like this in the results --->
Can you guys look at the CIDR value? Yes that's the whole subnet block dedicated to facebook today.
There you go, now you can use this process to get the IP block info about any of the big orgs like facebook. Now it's up to you how you guys use this info! Take care!!!
NetRange: 188.8.131.52 - 184.108.40.206 CIDR: 220.127.116.11/18 OriginAS: AS32934 NetName: FACEBOOK-INC NetHandle: NET-173-252-64-0-1 Parent: NET-173-0-0-0-0