ns-sec.ripe.net has one IP number , which also has a corresponding reverse pointer. ns4.ext.nic.fr and ns-ripe.6to4.nro.net point to the same IP. ont.es, tcd.ie, ip6.arpa, euro.net, dacht.net and at least 100 other hosts use this as a nameserver. ripe.net is a domain controlled by four nameservers. All of them are on different IP networks. Incoming mail for ripe.net is handled by two mailservers at ripe.net themselves. They are on the same IP network. ripe.net has one IP number. ns-sec.ripe.net is hosted on a server in Netherlands.