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I've been reading on AmazonWS that you use cname to use their webservices. Is CNAME when i have a file like this and then it really is at ? but the web user doesnt know this? he sees the url adress as in

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migrated from Oct 21 '10 at 0:30

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4 Answers 4

CNAME is used in DNS Name Resolution It simply tells the resolver to use the IP of another Domain Name that is already defined. It is nothing more as an alias, see also Justice's answer and the definition.

But it is not exchanged in the URL, the CNAME record is only used to lookup the IP of, and the original url is then used.

In your example it would be:

When the client is requesting, he first looks up the IP for The client asks a nameserver, and the nameserver sees a CNAME record in the DNS entry for that tells him to use the IP of let's say it is, so the nameserver returns to the client.

The Client now uses the original url and requests it from the web server at

In the DNS entry for there would somewhere be a line like:

sarah             3600  IN A

In the DNS entry for          3600 IN CNAME
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A CNAME record or Canonical Name record is a type of resource record in the Domain Name System (DNS) that specifies that the domain name is an alias of another, canonical domain name. This helps when running multiple services (like an FTP and a webserver; each running on different ports) from a single IP address. Each service can then have its own entry in DNS (like and Network administrators also use CNAMEs when running multiple HTTP servers on the same port, with different names, on the same physical host.

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CNAME is abbreviation for "Canonical Name", which is the 'official' name for the host or resource given.

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For more information you might be interested in some of the related RFCs.

RFC 1034 says "CNAME identifies the canonical name of an alias." In simple terms a CNAME is just an alias for a domain name, like a symbolic link to a file.

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