ns2.xs4all.nl has one IP number , which also has a corresponding reverse pointer. ns.hoho.nl, ns2.demon.nl and ns2.cistron.nl point to the same IP. rmi.nl, uni.nl, sbb.nl, bpv.nl, pro.nl and at least 100 other hosts use this as a nameserver. eth0.ns2.xs4all.nl are subdomains to this hostname. xs4all.nl is a domain controlled by two nameservers at xs4all.nl themselves. They are on the same IP network. Incoming mail for xs4all.nl is handled by four mailservers also at xs4all.nl. All of them are on the same IP network. xs4all.nl has two IP numbers. They are on the same IP network. ns2.xs4all.nl is hosted on a server in Netherlands.