There are three 'stages' to the DNS process: 1) Root Nameserver There are 13 of these servers and they store what domains have which nameservers. So when you look at this page the root nameserver has recieved a request for http://ed.vanbeinum.org and has responded by giving the nameservers as ns7.dotcolo.net and ns8.dotcolo.net. These nameservers know what to do with this request for http://ed.vanbeinum.org 2) The Nameserver This is a server that when you request a domain it looks up the correct IP address for that server. So when you you look at this page the nameserver has recieved a request for http://ed.vanbeinum.org, looked up that address and found the IP address of 188.8.131.52. There are always a primary and a secondary nameserver so there is a backup should the primary nameserver fail. 3) DNS settings on the nameserver These settings are stored on the nameserver and respond requests for email, websites, FTP and anything else you can think of. The DNS records at the nameserver provide information about what to do with these various requests. For example, these records can respond to a request for ed.vanbeinum.org or if a user at vanbeinum.org wants to send an email they have the records for where the email servers are for that domain. This incredibly flexible system allows myriad of setups. For example server2.vanbeinum.org could have an entirely different IP address and the mail server could be on yet another different IP address. DNS record types By no means a comprehaensive list, but the major record types are:
- A - these map a name to an IP address so ed.vanbeinum.org to 184.108.40.206 or another.vanbeinum.org to 78.45.567.123
- CNAME - these can get tricky if setup incorrectly but in general they map one server name to another. For example. this.vanbeinum.org to that.vanbeinum.org. This allows for that.vanbeinum.org to change its IP address and the CNAMe record will still work.
- MX - these specify where e-mail should be routed using the Simple Mail Transfer Protocol. They can only point to a name address and MUST NOT point to an IP address. For example an MX record may point to mailserver.vanbeinum.org but not 220.127.116.11. MX records also have a 'priorty' which allows several mail servers to be used as backups should the main mail server fail. Servers with the same MX proirity will share the workload equally between them