b1.audns.net.au has one IP number , but the reverse is adns1.berkeley.edu. adns1.berkeley.edu point to the same IP. au use this as a nameserver. audns.net.au is a domain controlled by nine nameservers. All of them are on different IP networks. Incoming mail for audns.net.au is handled by two mailservers at auda.org.au. They are on different IP networks. b1.audns.net.au is hosted on a server in United States even though the hostname implies Australia.