ns4.swisslink.ch has one IP number , which also has a corresponding reverse pointer. wtc.ch, sel.ch, cuk.ch, fsih.ch, vidas.ch and at least 100 other hosts use this as a nameserver. swisslink.ch is a domain controlled by four nameservers at swisslink.ch themselves. Some of them are on the same IP network. Incoming mail for swisslink.ch is handled by two mailservers also at swisslink.ch. They are on different IP networks. swisslink.ch has one IP number. ns4.swisslink.ch is hosted on a server in Switzerland.