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Background Setup Info


Web Server Name: web1

Server FQDN:

DNS Alias for FQDN: intranet

Browser URL: http://intranet/

Question 1: Is it possible then to setup a canonical sub-domain for this alias? Ex.


Question 2: If not, how about a new alias for a real sub-domain? Ex.

Sub-domain          DNS Alias         URL     intranetdocs      http://intranetdocs/

(Optional) The intention here is to prep our intranet site for serving up file attachments (MS Office, Adobe, etc.) from a separate domain, so that we might build a mini-cms app and keep the files out of the website (1998, I know)... any constructive advice/suggestions are welcome.

Why the downvotes? It's a pretty legit, on-topic question and relates directly to web software development (thousands of SO questions around DNS, domains, and routing).

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migrated from Jan 5 '12 at 20:25

This question came from our site for professional and enthusiast programmers.

Is your intranet site running on IIS 7+? – M.Babcock Jan 5 '12 at 0:26
It uses IIS 7.5 – one.beat.consumer Jan 5 '12 at 0:30
+1 to make up for someone's poorly communicated downvote (not mine). What you are after could generally be considered a reverse proxy. I've only lightly played with the Application Request Routing extension for IIS (only available for 7+), but here is a similar question from the forums. – M.Babcock Jan 5 '12 at 0:41

It's hard to tell what you're asking for here, however I'll try to answer it anyway. From what I see you have a web server with FQDN of web.blah.realTLD. First off I highly recommend against using a fake TLD and setup a subdomain for this, however you can't setup a Cname for the root of a DNS zone (RFC 1034). Your best option is to set an A record for docs.intranet to the IP address of the web server.

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What you call a "DNS Alias for FQDN" is probably nothing else than an alias from to

In general, you can leave out the domain for hostnames if the domain is in the search list of your DNS resolver. Therefore, http://‍intranet and http://‍web1 should both point to the same server (but not necessarily the same website, see Question 2 below).

Question 1

A name like docs.intranet will not work reliably.

Originally, resolvers would try the search list unless the domain name ended in a dot. With these resolvers, an alias such as docs.intranet would indeed work. However, this behaviour also means that the resolver would try to append the domains from the search list to any FQDN that is written without the final dot. For example, if someone want to access (instead of, the resolver would first try (which hopefully does not exist) and only then, causing a small and unnecessary delay.

For this reason, many resolvers now only apply the search list if the domain name does not * contain* a dot. This means that will be looked up directly as because it contains a dot. With these resolvers, docs.intranet will be treated as docs.intranet., which does not exist.

Question 2

You don't need to add another subdomain. Just set up intranet-docs (or whatever name you prefer) as an additional alias for

However, setting up an alias in the DNS is only half of the configuration. The DNS alias only means that the browser will contact the correct machine when you access http://‍intranet-docs.

As a second step, you'll need to tell the web server running on that machine what to do with a request for that name. That is, you will have to configure a new virtual host (with intranet-docs as an alias) in IIS. Please note that the name the web server sees as the name of the virtual host is the name used in the URL, not the canonical name used in the DNS.

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