pns.ocn.ad.jp has one IP number , which also has a corresponding reverse pointer. ntt.com, ddk.co.jp, ndc.co.jp, itoh.co.jp, himono.com and at least 100 other hosts use this as a nameserver. uss.co.jp use this as a mailserver. ocn.ad.jp is a domain controlled by two nameservers at ocn.ad.jp themselves. They are on different IP networks. Incoming mail for ocn.ad.jp is handled by two mailservers also at ocn.ad.jp. They are on the same IP network. ocn.ad.jp has two IP numbers. They are on the same IP network. pns.ocn.ad.jp is hosted on a server in Japan.