ns03.usen.ad.jp has one IP number , which also has a corresponding reverse pointer. enag.net, cs-tv.net, usen.co.jp, ucom.ne.jp, gate01.net and at least 100 other hosts use this as a nameserver. usen.ad.jp is a domain controlled by three nameservers at usen.ad.jp themselves. All of them are on the same IP network. Incoming mail for usen.ad.jp is handled by two mailservers also at usen.ad.jp. They are on the same IP network. ns03.usen.ad.jp is hosted on a server in Japan.