We pick c.root-servers.net, one of the 13 root servers (1), and ask it about biz.biz.pl and learn that pl is delegated to eight name servers (2), so we ask f-dns.pl where we learn that biz.biz.pl is delegated to two name servers, including ns1.premium.pl (3), so we ask that one and get the following answer:
The two name servers ns1 and ns2.premium.pl together
There are several thousand of domains that use name server group 1.
Three quarter of those point only to the IP number 62.129.243.50 (example: firemki.pl, fotopoznan.pl and usz.pl ). Worth noting is that most of the host names that point only to the IP number 62.129.243.50 use name server group 1.
At least one of them point only to the IP number 178.33.0.21.
The IP number 62.129.243.50 only
Most of the several thousand of host names that point only to the IP number 62.129.243.50 use name server group 1 (example: atmosfera.pl, przeprowadzki.olsztyn.pl and lokalizuj.pl ). Worth noting is that three quarter of the domains that use name server group 1 point only to the IP number 62.129.243.50.