You will require a single dedicated IP which has to be allotted as a main shared ip for your reseller account.
MDC or Multidomain SSL Certificate will allow you to install SSL certificates for multiple domains under your reseller account. Google page ranks and other SEO techniques will provider better results with SSL enabled in a domain name.
Traditionally, SSL requires a Dedicated IP for each domain name. When viewed in a SSL analyser it will show the domain name, ip and the certificate issuer.
But buying dedicated ip for each of the domain name under your reseller account is very costly. Hence in MDC SSL, all you have to do is to buy a single dedicated ip and make it as a main shared ip for your reseller account. Then install MDC SSL for the domains under your reseller account. This way in a SSL analyzer only show domains under your reseller account with the same shared ip.