What you call a "DNS Alias for FQDN" is probably nothing else than an alias from
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).
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
www.google.com (instead of
www.google.com.), the resolver would first try
www.google.com.abc.gov.ca (which hopefully does not exist) and only then
www.google.com., 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
www.google.com will be looked up directly as
www.google.com. because it contains a dot. With these resolvers,
docs.intranet will be treated as
docs.intranet., which does not exist.
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
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.