We pick l.root-servers.net, one of the 13 root servers (1), and ask it about yahoo.pk and learn that pk is delegated to three name servers (2), so we ask root-s.pknic.pk where we learn that yahoo.pk is delegated to four name servers, including ns2.yahoo.com (3), so we ask that one and get the following answer:
Yahoo.pk is a domain controlled by four domain name servers at yahoo.com. All four of them are on different IP networks. Incoming mail for yahoo.pk is handled by one mail server at .. We are missing the IP:s of one server: .. Yahoo.pk has two IP numbers (126.96.36.199, 188.8.131.52). Both are on different IP networks.
The five name servers ns1, ns2, ns3, ns4 and ns5.yahoo.com together
Three quarter of the more than hundred domains that use name server group 1 point to IP group 1 (example: altavista.ch, altavistausa.com and altivista.com ). Worth noting is that most of the host names that point to IP group 1 use name server group 1.