50.88.84.in-addr.arpa is delegated to three nameservers, however one extra nameserver is listed in the zone. All of them are on the same IP network. bsc.es, res.es, icc.es, uic.cat, udg.edu and at least 31 other hosts share nameservers with this domain. 88.84.in-addr.arpa is a domain controlled by three nameservers. Two of them are on the same IP network.