We pick l.root-servers.net, one of the 13 root servers (1), and ask it about 12.1.0.194.in-addr.arpa and learn that in-addr.arpa is delegated to six name servers (2), so we ask b.in-addr-servers.arpa where we learn that 194.in-addr.arpa is delegated to six name servers, including tinnie.arin.net (3), so we ask that one and learn that 1.0.194.in-addr.arpa is delegated to two name servers (4), so we ask ns6.icb.co.uk and get the following answer:
