We pick j.root-servers.net, one of the 13 root servers (1), and ask it about isac.cnr.it and learn that it is delegated to six name servers (2), so we ask a.dns.it where we learn that cnr.it is delegated to four name servers, including dns.cnr.it (3), so we ask that one and learn that isac.cnr.it is delegated to four name servers (4), so we ask jolly.bo.cnr.it where we see a CNAME from isac.cnr.it to sky.isac.cnr.it, so we have to start all over again. We already know that d1.ira.cnr.it is authoritative for isac.cnr.it (5) and ask it about sky.isac.cnr.it and get the following answer:
Isac.cnr.it is a domain controlled by five domain name servers at cnr.it and inaf.it having a total of nine IP numbers. Some of them are on the same IP network. Incoming mail for isac.cnr.it is handled by one mail server at cnr.it having a total of two IP numbers. Both are on different IP networks.