74.184.83.in-addr.arpa is a domain controlled by two nameservers at dns.swip.net. They are on different IP networks. lo.se, do.se, gp.se, skk.se, lfv.se and at least 100 other hosts share nameservers with this domain. 184.83.in-addr.arpa is a domain controlled by four nameservers. All of them are on different IP networks.