DNS Question(CNAME)?

Question

Can someone please explain what a CNAME record is used for? I don't understand. Also how does it differ from the A record? Thanks.

Answer 1

CNAME is a canonical name reference. It basically inherits all properties of another domain's records. Because of this, you can't have any A Record, MX, etc. It's doubtful that you will use this. I'd stick with A Records. A Records are what are actually used to point the name to your IP address where your site, mail server, etc., is hosted.

Answer 2

The CNAME is the canonical name. The word is misleading, a canonical name generally indicates the real name of the machine. In internet dns terms, the cname is used to create an alias. You may have a machine with a real name mypc.mynetwork, it may call itself mypc.my.domain.com in the web server, this is possibly the registered name in dns. This machine may need to serve mail, web, ftp and network file services. You are not going to advertise file services. The came records would look as below :
www IN CNAME mypc.my.domain.com.
mail IN CNAME mypc.my.domain.com
ftp IN CNAME mypc.my.domain.com.

Don't make the error as at line 2, no . at the end, this will look up :
mypc.my.domain.com.my.domain.com - does not exist.
The same machine now has 3 aliases, this is how 95% of the macines on the internet are named. If a server goes down and a standby backup is available called backup.my.domain.com it can sit on the internet invisible until the failure, then changing the cname records :
www IN CNAME backup.my.domain.com.
makes it instantly visible, the failed machine disappears.