ns-jp.sinet.ad.jp has one IP number , which also has a corresponding reverse pointer. f.dns.jp point to the same IP. kyoto-econ.ac.jp use this as a nameserver. sinet.ad.jp is a domain controlled by two nameservers at sinet.ad.jp themselves. They are on the same IP network. Incoming mail for sinet.ad.jp is handled by three mailservers also at sinet.ad.jp having a total of four IP numbers. Two of them are on the same IP network. sinet.ad.jp has one IP number , but the reverse is jpnac.sinet.ad.jp. ns-jp.sinet.ad.jp is hosted on a server in Japan.