SSL/TLS and Shared IP Addresses

Plesk supports the Server Name Indication (SNI) extension to the
Transport Layer Security protocol, which makes it possible to use
authentic SSL/TLS certificates for sites hosted on shared IP addresses.

SNI helps to efficiently use IPv4 resources and provides the following
benefits:

• Providers can run any number of SSL/TLS sites with independent
  certificates on a single IPv4 address.
• Hosting customers can install independent SSL/TLS certificates on
  each of their sites; therefore, there is no need to purchase another
  subscription. Each customer can install an SSL/TLS certificate even
  if there is only one shared IP address on the whole server.

The SSL/TLS support with SNI is possible only if the following
requirements are met:

• The operating system of your Plesk server supports SNI.

  • Linux systems (see the full list in the release
    notes).
  • Windows 2012.

• Users’ browsers support SNI.

  Most modern web browsers, starting with IE 7, Firefox 2.0, Opera 8.0,
  and Chrome 1.0, support SNI, unless they are run on Windows XP.
  Learn more about SNI
  and the client software that supports it.

By default, on clean Plesk installations (Linux and Windows), the
support for SNI is turned on.

If SNI is not supported and you (as the administrator) assign an SSL/TLS
certificate to a site hosted on a shared IP address, Plesk will
associate that certificate with all other sites hosted on this IP
address. In the same case, hosting customers with shared IP addresses
will not be able to assign SSL/TLS certificates to their sites: the page
Websites & Domains > <domain_name> > SSL/TLS Certificates
will be hidden in their Customer Panel.

For instructions on assigning SSL/TLS certificates to websites, refer to
the section Securing Connections with SSL/TLS
Certificates.