I came across this problem whilst setting up a UAT environment at work. Having not dealt with SSL certs before, especially on the older IIS6, it was actually a little challenging to figure out.
What’s the Problem?
It turns out that when using SSL, you can only have one website bound to one IP address at a time. Lame. Luckily you can get around this, as long as your websites all use the same certificate, a wildcard certificate.
Trying to configure and start two sites using the same cert, port and certificate will result in this error:
IIS was unable to start the site. Another site may already be using the port you configured for this site. Please select a unused port for this site.
The Solution: Enable Multiple SSL Bindings
I’m not sure if this is purely an IIS6 problem, but to solve it we need to go to the command line.
Whip open a command prompt and navigate to the following location:
C:\inetpub\adminscripts\. If this location doesn’t exist and/or it doesn’t contain a file named adsutil.vbs then follow these instructions to Install Missing IIS Admin Scripts before moving on.
Now, still in the C:\inetpub\adminscripts\ folder, enter the following command for each website that you would like to bind:
cscript.exe adsutil.vbs set /w3svc/<site identifier>/SecureBindings ":443:ssl1.example.com"
The <site identifier> can be found by clicking the Web Sites folder icon on the left hand menu in IIS6 as shown below:
Of course ssl1.example.com should be replaced with your own host header.
That’s It. You should now be able to start both websites successfully.