You may need to map multiple web sites with the same port number or you may want to map an IP address that has been set to a netscaler vip/ip to multiple servers. IIS 6.0+ allows you to do that with a feature called Host Header Names. For the official details, review Microsoft's web site: http://support.microsoft.com/kb/324287
Here's how it works:
Let's say you have a DNS entry called MetroDesignDev.LoadBalanced.Twins.com @ ip address: 10.201.25.216 and one of the load balanced twins (ServerAlphaTwin) has an address of 10.201.25.111 and the other (ServerBetaTwin) has an address of 10.201.25.112.
To set this up on the ServerAlphaTwin you would do the following:
1. Click Start> Administrative Tools, and then click Internet Information Services (IIS).
2. Where you see the name of the server (in this case ServerAlphaTwin), expand Web Sites.
3. Right-click the Web site that you need to change (usually Default Web Site), click on Properties.
The Properties dialog box will appear--once it does do the following:
4. Click on the Web Site tab, click Advanced.
5. Under Multiple identities, click the IP address, and then click Edit.
When the Advanced Web Site Identification dialog box is up:
6. Under the Host Header Name, type the host header that you want. In this case, type MetroDesignDev.LoadBalanced.Twins.com
7. Add the port number (usually 80)
8. Select the IP address in the list if there, if not type it in. In this case it would be (10.201.25.216) and then click OK.
What you will see in this dialog box for ServerAlphaTwin is:
IP Address TCP port Host Header Value
10.201.25.111 80 <default>
10.201.25.216 80 MetroDesignDev.LoadBalanced.Twins.com
For ServerBetaTwin repeat steps 1-9, replacing the ip addresses accordingly.
What you will see in the Advanced Web Site Identification dialog box for ServerBetaTwin is:
IP Address TCP port Host Header Value
10.201.25.112 80 <default>
10.201.25.216 80 MetroDesignDev.LoadBalanced.Twins.com
So now both the Alpha and Beta servers can be accessed by addressing the MetroDesignDev.LoadBalanced.Twins !