We pick c.root-servers.net, one of the 13 root servers (1), and ask it about 31.hk and learn that hk is delegated to ten name servers (2), so we ask t.hkirc.net.hk where we learn that 31.hk is delegated to four name servers, including ns4.ns365.net (3), so we ask that one and get the following answer:
31.hk is a domain controlled by four domain name servers at ns365.net and gzidc.com having a total of eight IP numbers. Some of them are on the same IP network. 31.hk has one IP number (113.10.144.115), but the reverse is ?.
All of the more than hundred domains that use the primary name server ns3.gzidc.com use the two name servers ns3 and ns4.gzidc.com together (but neither ns3 nor ns4.ns365.net ), hereafter referred to as "name server group 2", (example: dmwz168.com, it0753.com and kangyilr.com ). Worth noting is that three quarter of the domains that use name server group 2 use the primary name server ns3.gzidc.com.
The two name servers ns3 and ns4.gzidc.com together
There are more than hundred domains that use name server group 2.