In a real-world production environments, there can be multiple web applications in the same farm that use different host headers but the same port, which is often 80/443. This is not an issue when SSL is not implemented. When the request reach the web server, IIS will direct the request to specific sites based on the host header. However, if SSL is to be implemented and all the sites will be using the same port, there will be a problem with the certificate as network end-point can only be identified with IP:Port binding. In the old days, two possible solutions are:
- Use two IPs on the same server, so that each IIS site can use a different certificate. This is should not be too difficult when the WFEs are virtualized.
- Use a wildcard certificate so all the web applications can use the same certificate as long as they share the same domain. If not, you may want to choose a Unified Communications Certificate if that really is a preferred solutions in your situation.
With Windows Server 2012 or above, you have the third option that comes with the Server Name Indication feature of IIS 8. This feature makes it possible that the host name in the IIS binding be used to identify the network endpoint. In this case, different IIS sites can use the same IP address and port while using different certificates. However, it requires the client browsers to support SNI. If not, you need to create a default SSL site. Check this blog post for more information: http://blogs.msdn.com/b/kaushal/archive/2012/09/04/server-name-indication-sni-in-iis-8-windows-server-2012.aspx