In brief, if you want to host multiple sites (on IIS) – and all you have is a single IP , you have to use host-headers (in IIS). These host headers will identify the incoming target website and IIS can appropriately redirect to the appropriate target. However, if your sites require SSL, there is no way to accomplish this with a single IP (assuming each site has it’s own certificate).
Wildcart SSL Cert
A potential workaround is to use a wildcard cert – which would allow multiple site bindings to a single IP.
Multiple IP addresses – Single Server
Of course, if you are not restricted from assigning additional IPs on the same server, you are all set. All you need is a unique IP for each website that you are hosting.
Cloud and Virtual IPs
In the cloud world, obtaining VIPs (Virtual IPs) for the same instance is a piece of cake. This makes hosting multiple sites on the same instance trivial in the cloud. Each site can have it’s own SSL cert or use a wildcard cert across all sites.