We pick m.root-servers.net, one of the 13 root servers (1), and ask it about castetner.fr and learn that fr is delegated to five name servers (2), so we ask d.ext.nic.fr where we learn that castetner.fr is delegated to two name servers, including sdns2.ovh.net (3), so we ask that one and get the following answer:
Castetner.fr is a domain controlled by two domain name servers at ovh.net and logipro.com having a total of three IP numbers. All three of them are on different IP networks. Incoming mail for castetner.fr is handled by three mail servers at castetner.fr themselves having a total of 33 IP numbers. Two mail servers have the same IP number. Some of them are on the same IP network. Castetner.fr has one IP number (91.121.57.171), but the reverse is 91-121-57-171.logipro.com.
