Enable external health check for UDP and non-HTTP virtual servers

Last published : Sep 24, 2026
In public clouds, you can use the NetScaler appliance as a second-tier load balancer when the native load balancer is used as the first tier. The native load balancer can be an application load balancer (ALB) or a network load balancer (NLB). Most of the public clouds do not support UDP health probes in their native load balancers. Hence, if these servers are down their actual status might not be updated. As a result, traffic is sent unconditionally to NetScaler, even if the request cannot be serviced. To monitor the health of such applications, NetScaler supports HTTP and TCP health checks.
An HTTP or TCP listener is created for a content switching virtual server when both the probeProtocol and probePort parameters are configured. The listener reflects the status of the virtual server. The ProbeSuccessResponseCode parameter applies only to HTTP and returns the configured string when the probe is successful.
Related information

To enable external health check for UDP and non-HTTP TCP virtual servers by using CLI

At the command prompt, type:
add lb vserver <name> <serviceType> <IPAddress> <port> -ProbeProtocol <HTTP/TCP> -ProbePort <port-num> -ProbeSuccessResponseCode<http-code>
Example:
add lb vserver Vserver-UDP-1 HTTP 10.102.29.60 80 -ProbeProtocol TCP -probeport 5000 -probesuccessResponseCode 200ok

To enable external health check for UDP and non-HTTP TCP virtual servers by using GUI

  1. Navigate to Traffic Management > Load Balancing > Virtual Servers, and then create a virtual server.
  2. Click Add to create a virtual server.
  3. In the Basic Settings pane, update the following details:
    1. Probe Protocol –Select the protocol (HTTP or TCP) of the probe for external health check of the virtual server.
    2. Probe Success Response Code –Enter the response string for a successful probe. This parameter is applicable only for the HTTP protocol.
      • Default Value: 200ok
      • Maximum Length: 63
    3. Probe Port –Enter the port number for HTTP or TCP monitoring.
  4. Click OK.