The Domain Name System (DNS) is not difficult to understand, but you do have to take a little time to learn some of the rules. Basically, DNS is used on the Internet to map names to IP addresses. A mapping is simply an association between a system name (e.g. www.clearcenter.com) and a system's IP address (e.g. 126.96.36.199). However, different services use different types of mappings or records. The example below will walk you through a configuration for a typical server.
Let's go through a typical example. You have just registered example.com as your domain.
The DNS configuration for this set up is shown in the table below. Don't worry about the details yet… keep reading!
|example.com||188.8.131.52 (your primary server)|
|mail.example.com||sample.com Don't do this… see why below|
|example.com||example.com (not intuitive!)|
The bread and butter behind the DNS system is the A Record. The A record (address record, or host record) maps a domain name to an IP address on the Internet.
In our example, the ClearOS system is hosting example.com. Using the Dynamic DNS tools, you would set your domain to be example.com and the IP address (184.108.40.206) will be automatically updated via dynamic DNS. For your camera, you need to create a static A record with the IP address (220.127.116.11) associated with camera.example.com.
So, you have two names mapped to IP addresses (A Records):
CNAME Records (Canonical Name records) act as aliases for hostnames. Instead of mapping a domain name to an IP address (an A record) you can map a domain name to another domain name. In the example, you have:
What are the advantages of CNAMEs? You can map multiple domain names mapped to one - sometimes dynamic - IP address. In our example, files.example.com and www.example.com will now be associated with example.com's IP address (our first Dynamic DNS A record). In the case of the remote office, you change a not-so-easy-to-remember-super-long domain name into something better.
MX Records (Mail eXchanger record) tells mail systems how to handle mail that is addressed to a particular domain. Like CNAME records, the MX record maps a domain name to another domain name.
In the example, we use our primary machine as a server for mail to email@example.com. Every MX record is tagged with a priority number. The MX record with the lowest number is the primary mail server. If the primary server is unavailable, the backup mail server (also called a “secondary mail server”) will queue the mail. You can use the ClearCenter Mail Backup service sto backup your mail when your network is offline.