In IIS 6.0, we are trying to set up a DNN installation where each portal is secured with a different security certificate.   Our first portal is assigned as a separate IIS website, uses the same I.P., port 80 and ssl port 443,  and uses it's OWN host headers.   We then installed the first certificate for site1.com and it worked fine.

We then set up a second portal, as a second IIS website with the same I.P., port 80 and ssl port 443, but with DIFFERENT host headers.   We installed the security certificate for site2.com, but it is reading the certificate for site1.com.  

Has anyone successfully setup a multiple portal DNN installation that uses a different SSL cert on each portal?   It will be infeasible for us to user a separate IP address for each portal.

It seems that as acquiring a unique IP address for every site could be difficult, wouldn't using a different port be more beneficial?  Are there any drawbacks to using different ports for every IIS website?

The requirement is that you can only have one SSL certificate assigned to a single IP address & Port combination. 

The web server listens on a specific port for incoming traffic, and then depending on what certificate is assigned, that is the one it will use.

If you assigned two different IIS websites to the same IP address and port then one is not working.  
Once the port is opened on an IP then no other sites can open the same port on that IP.

I mentioned earlier that you can not do it with Host Headers. I hope that part is clear.

The problem with using different ports is that you will have to send users to a url that has that port in it (eg https://www.yoursite.com:444).  
Not that it can't be done, but you just have to be real careful to make sure you are on the right port.