Overview

SNI (Server Name Indication) support was added in IIS 8. It allows you to have multiple HTTPS certificates on the same IP address. Without it, you can only use a single certificate per IP address.

Options

If you want to have SSL for multiple sites with multiple domains with IIS 7.5 or lower all binded to the same IP address your choices are:

1. Create a single certificate for all sites, which only works if there are less than 100 in total (that's the maximum Let's Encrypt will currently support)
2. If they are sub domains of the same root, a wildcard certificate can be an options.
3. Upgrade to IIS 8+

Configuring the IP Address Binding

When win-acme creates the binding for a new certificate, it will bind the wildcard (*) IP address by default. In other words, all IP addresses will be bound to the new certificate for HTTPS. This can be customized with the --sslipaddress switch from the command line.

If you have multiple IP addresses and want to bind different certificates to each, you must manually change the IP address for the SSL binding after installing a new certificate with win-acme. Thereafter, when renewing the certificate, win-acme will preserve the IP address of the binding.

.NET Requirements

.NET Framework 4.7.2 is a minimum system requirement, which means the program can run on Windows Server 2008 R2 SP1 or above. Some users have reported success running .NET Framework 4.7.2 and WACS on Windows Server 2008, though that is not supported by Microsoft.