Domain Concepts


DNS Records

CNAME or "Canonical Name"

(CNAME) Record is used to define an alias hostname. A "CNAME" record takes this format:      IN     CNAME

This defines as an alias for the host whose canonical (standard) name is

"A" Record

An A record gives you the IP address of a domain. That way, users that try to go to will get to the right IP address. An A record or "Address Record" maps a hostname to a 32-bit IPv4 address. An "A" Record takes this format (example):

Name             TTL     TYPE    DATA   43200   A       IP Address


DNS Zone files are written with a "wildcard" entry, that looks like this:

*   IN   A


The x's represent your particular IP address. The star takes "anything" and points it to your server's IP address. This way, if someone mistakenly types too many or too few w's, they'll still see your website. This is also useful for setting up subdomains on your server, relieving you of the duty of adding an additional "A" record for the subdomain.

MX Record

Mail Exchange Record: Maps a domain name to a list of mail exchange servers for that domain. A zone can have one or more Mail Exchange (MX) records. These records point to hosts that accept mail messages on behalf of the host. A host can be an 'MX' for itself. MX records need not point to a host in the same zone. An 'MX' record takes this format:       IN     MX      10


IN     MX      20


The 'MX' preference numbers nn (value 0 to 65535) signify the order in which mailers select 'MX' records when they attempt mail delivery to the host. The lower the 'MX' number, the higher the host is in priority.

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