Iis – Setting up a domain name to use host headers

You will need to create records in your DNS for the new web site names, referring to the IP address that the web farm answers for.

The "Host Header" is the host and domain name entered in the "Address" bar of the browser. (Beware that both the fully-qualified and unqualified names need to be entered as host hedaers if the users will be using both.) Configure host header entries on each of the web servers in the farm for the new web site names, listening on whatever IP address the load balancing solution will send incoming requests to.

If DNS is directing clients to the farm IP address and all the farm web servers have the proper host headers entered things should work as you expect.

Since you're relying on the domain name rather than IP (which is easier in this situation), here's the most straight forward way of doing this:

• make sure that your outside-facing server has bindings for the 3 sites based on the host header (website1.mydomain.com, etc). You can leave the IP address as (All unassigned). You probably have this done already. -- Basically what I mean is to add a binding to the first site that is "website1.mydomain.com", and to the other two sites in a similar way. Here's a walkthrough on bindings.

• create 2 Web Farms in ARR on the ARR server. One to internalserver and the other to internalserver2. Use the primary IPs of those servers. You can setup 3 different Web Farms if you want unique health checks for each website. It's ok that two of them point to the same server. -- Steps: Create a new Server Farm called InternalServer and add a single server to it, which is "internalserver". Then create another Server Farm called InternalServer2, and add just "internalserver2" to it.

• on the last step of the wizard when creating the site, when it asks if you want ARR to create a rule for you, only say 'yes' the first time. Take note of the rule that it creates so that you can learn from it. Then delete it. You want to manage your own rules. -- I'll explain the rules in the next step.
• you should then set 3 URL Rewrite rules at the global level (IIS Server node, not the website node). URL = .*, use a condition with {HTTP_HOST} for your domain name, and the action should route to the corresponding webfarm. -- Here's an intro to URL rewrite. Follow those steps and enter a rule like the one below:

Example URL Rewrite:

<rule name="site1" patternSyntax="ECMAScript" stopProcessing="true">
  <match url=".*" />
  <conditions logicalGrouping="MatchAll">
    <add input="{HTTP_HOST}" pattern="^website1\.mydomain\.com$" />
  </conditions>
  <action type="Rewrite" url="http://InternalServer1/{R:0}" />
</rule>