23.0.66.in-addr.arpa is a domain controlled by two nameservers at deltacom.net. They are on different IP networks. bti.com, acc.edu, mahl.com, acc1.edu, msar.org and at least 57 other hosts share nameservers with this domain. 0.66.in-addr.arpa is delegated to two nameservers, however one extra nameserver is listed in the zone. All nameservers are also at deltacom.net. All of them are on different IP networks.