DNS or Domain Name System gives the Internet its identity. Every website URL and email address is linked to an IP address, and DNS is the system that translates the IP into a domain.
When you setup DNS zone records on your server, there are various types you will encounter:
A – An A record is the “host record” The hostname is directly mapped to the IP address with this record.
Example: www IN A 199.999.99.99
CNAME – A Canonical Name record serves as an alias for another record. With it, a website can essentially have two or more hostnames. You might want to have ftp.yourdomain.com and www.yourdomain.com, one for the FTP server and one for the website, but in reality, they point to the same IP address.
Example: ftp IN CNAME yourdomain.com.
You can also use it to point to another domain name entirely, which is especially useful for cloud computing services, such as Google Apps.
Example: mail.yourdomain.com IN CNAME mail.cloudmail.net.
(Notice that the domain name ends with a period in the zone record)
NS – A Name Server is the authoritative DNS server for your domain. Every domain must have at least two, and each one should point to a different physical server.
Example: dns1.nameserver.com dns2.nameserver.com
MX – These are the mail server records. Like CNAME, they can either point to your domain or to any other that accepts mail for you (i.e. cloud server).
Example: @ IN MX 10 yourdomain.com.
Example: @ IN MX 20 mailserve.cloudmail.net.
There are other important records to know, such as SOA and reverse DNS. We will cover those next week.