ns-ext.vix.com has one IP number , but the reverse is ns-ext.isc.org. c.nic.so and ns-ext.isc.org point to the same IP. ug, ro, np, ao, bg and at least 86 other hosts use this as a nameserver. vix.com is a domain controlled by four nameservers. All of them are on different IP networks. Incoming mail for vix.com is handled by one mailserver at vix.com themselves. vix.com has one IP number. ns-ext.vix.com is hosted on a server in United States.