Referring to FAQ1057 "How do I configure reverse proxy?" and document Reverse Proxy with SSL (https://bto.bluecoat.com/doc/8412), this FAQ further describes the requirements and steps to create multiple HTTPS domains as HTTPS reverse proxy.
After the first HTTPS keyring is assigned to an HTTPS Reverse Proxy service on the ProxySG, and working successfully, you will be required to create another HTTPS Reverse Proxy Service on the ProxySG in order to differentiate it from the first one.
Either a different IP address (or VIP) is required, or a different destination port, which in this case might be port 443 or 444.
With each additional backend HTTPS server host, you require to create additional VIP and Keyring on the proxy.
Creating a VIP:
From the Management Console, select Configuration > Network > Advanced > VIPs.
Note: VIP must be routable within the same subnet of the physical IP of the proxy.
Creating an Additional HTTPS Reverse Proxy Service:
From the Management Console, select Proxy Services > HTTPS Reverse Proxy Services > Proxy settings.
Set the Keyring as your design for the respective HTTPS domain.
Set other attributes as necessary.
Select the Proxy Services > HTTPS Reverse Proxy Services > Listener tab.
Set the Destination host as the VIP (configured previously) of the ProxySG.
This enables the proxy to intercept the respective traffic and forward it to the correct HTTPS server host.
In addition, you must complete the following tasks:
1) Create forwarding hosts for the subsequent HTTPS domain hosts.
2) Allow access to the subsequent HTTPS domains.
3) Create and define the forwarding rule for the subsequent HTTPS domains.
Refer to the steps in the following Reverse Proxy with SSL article: https://bto.bluecoat.com/doc/8412.