websites become non-functional and gives error "page cannot be displayed" 

Should enable SNI while binding all the certificates to the specific vserver whether wildcard or server certificate 



Additional information : 


Starting with NetScaler software release 9.2, you can enable the SNI feature of the appliance to host multiple domains securely on a single Secure Socket Layer (SSL) virtual server IP address. The SNI feature enables the client requesting a connection to specify the server secure domain. As a result, you need not configure multiple virtual servers to host multiple domains, listening on multiple IP addresses and port numbers.

The SNI feature enables you to bind multiple certificates to a single virtual server. This is in contrast to the wildcard certificates, which refer to subdomains within a domain and not individual domains similar to the SNI feature. However, you can specify subdomains in the SNI feature too. Internally, the NetScaler appliance parses the certificates and extracts domain names. The appliance stores these domain names in a hash table.

You can also bind the default certificates to the virtual server. The default certificate is used for the client that does not specify the domain name because some web browsers do not send the domain name. In such scenarios, the appliance responds to the client with the default certificate.

The following is the command to bind an SNI certificate to a virtual server:
bind sslvserver <VServer_Name> -certkeyname <Domain_Name> -SNICert

Problem Cause