ns2.sentia.nl has one IP number , which also has a corresponding reverse pointer. ns2.pongnet.nl point to the same IP. bl.nl, bie.nl, subaru.be, sentia.nl, subaru.nl and at least 100 other hosts use this as a nameserver. sentia.nl is a domain controlled by two nameservers at sentia.nl themselves. They are on different IP networks. Incoming mail for sentia.nl is handled by two mailservers also at sentia.nl. They are on different IP networks. sentia.nl has one IP number. ns2.sentia.nl is hosted on a server in Netherlands.