We have a content switch in front of a virtual server in NetScaler ADC, and it acts as a load balancer. It is tied to a service group that has an HTTP monitor. We cannot get this monitor to work.
The monitor calls an HTTPS endpoint. The endpoint expects a SNI extension (Server Name Indication) in the Client Hello TLS handshake from the NetScaler. The NetScaler doesn’t add this, according to our traffic dump. This causes the endpoint to fail (it sends an error code in its TLS reply packet, and then the NetScaler sends a client reset packet.)
Why doesn’t our NetScaler send the SNI extension?
Screenshots are attached of the service group configuration:
the monitor configuration:
the SSL profile used in both the service group and the monitor:
and output of our capture - the packet sent by the NetScaler - no SNI extension sent:
