ns2.domain21.com has one IP number , which also has a corresponding reverse pointer. ns2.oseo.co.kr point to the same IP. kwkim.net, vreve.com, satto.com, mulga.net, msdog.com and at least 100 other hosts use this as a nameserver. domain21.com is delegated to three nameservers, however two delegated nameservers are missing in the zone. All nameservers are at domain21.com themselves. All of them are on the same IP network. ns2.domain21.com is hosted on a server in Korea.