We pick l.root-servers.net, one of the 13 root servers (1), and ask it about cdns.net and learn that net is delegated to 13 name servers (2), so we ask f.gtld-servers.net where we learn that cdns.net is delegated to three name servers, including ns3.icb.co.uk (3), so we ask that one and get the following answer:
The four name servers ns0, ns1, ns2 and ns9.inone.com together
All of the three domains that use the four name servers ns0, ns1, ns2 and ns9.inone.com together, hereafter referred to as "name server group 1", point only to the IP number 91.208.95.197.
The three mail servers mx2.communitydns.net, serv141.icb.co.uk and srvc131.icb.co.uk together
All of the six domains that use mail server group 1 point to the three IP numbers 2001:470:1f08:170e:1::102, 91.208.95.198 and 193.223.78.102 together, hereafter referred to as "IP group 1". Worth noting is that six of the host names that point to IP group 1 use mail server group 1.
The three IP numbers 2001:470:1f08:170e:1::102, 91.208.95.198 and 193.223.78.102 together
Six of the eight host names that point to IP group 1 use the three name servers ns1.inone.com, ns1.communitydns.net and ns3.icb.co.uk together, hereafter referred to as "name server group 2". Worth noting is that six of the domains that use name server group 2 point to IP group 1.
The name server ns1.inone.com
Three of the eleven domains that use the name server ns1.inone.com use name server group 1.