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How to get a secure HTTP monitor to send SNI in its request?


Go to solution Solved by Martin Ørding-Thomsen,

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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 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:

servicegroup.png.e258a03117a6bbf994cc67a6025ae8b1.pngthe monitor configuration:

monitorconfiguration.png.951a7d75289be7e3757cbabe5cdb1dc1.pngmonitorconfigurationadvancedparameters.png.589a0c1292bc2ff33e179c594c26dae1.pngthe SSL profile used in both:

sslprofileknyttettilservicegroup.png.51c9ab9db611f6814f6e88a791b216d0.pngand output of our capture - the packet sent by the NetScaler - no SNI extension sent:

capture.png.6937932c72510835b1cec674fc9d5054.png

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