ns.swan.sk has one IP number , which also has a corresponding reverse pointer. ns.callino.sk point to the same IP. pkb.sk, san.sk, szpm.sk, zkssr.sk, scnet.sk and at least 54 other hosts use this as a nameserver. fwa26.sk, belar.sk and milosh.info use this as a mailserver. root.ns.swan.sk are subdomains to this hostname. swan.sk is a domain controlled by two nameservers at postel.sk. They are on the same IP network. Incoming mail for swan.sk is handled by two mailservers at swan.sk themselves. They are on different IP networks. ns.swan.sk is hosted on a server in Slovakia.