ns1.rug.nl has one IP number , but the reverse is mailhost.rug.nl. ns1.gn-ix.nl and mailhost.rug.nl point to the same IP. rug.nl, usor.nl, ai.rug.nl, id.rug.nl, ub.rug.nl and at least 100 other hosts use this as a nameserver. rug.nl is a domain controlled by three nameservers. Two of them are on the same IP network. Incoming mail for rug.nl is handled by two mailservers having a total of three IP numbers. Two mailservers have the same IP number. Two of them are on the same IP network. ns1.rug.nl is hosted on a server in Netherlands.