We pick m.root-servers.net, one of the 13 root servers (1), and ask it about static.thefacebook.com and learn that com is delegated to 13 name servers (2), so we ask c.gtld-servers.net where we learn that thefacebook.com is delegated to two name servers, including b.ns.facebook.com (3), so we ask that one where we see a CNAME from static.thefacebook.com to s-static.t.facebook.com, so we have to start all over again. We already know that b.gtld-servers.net is authoritative for com (4) and ask it about s-static.t.facebook.com and learn that facebook.com is delegated to two name servers (5), so we ask a.ns.facebook.com where we learn that t.facebook.com is delegated to two name servers, including a.ns.t.facebook.com (6), so we ask that one and get the following answer:
All of the four host names that point to the IP number 69.171.235.9 point to the two IP numbers 69.171.235.9 and 69.171.246.9 together, hereafter referred to as "IP group 1".
The IP number 69.171.246.9
All of the four host names that point to the IP number 69.171.246.9 point to IP group 1.