Enable external TCP health check for UDP virtual servers

Last published : Sep 22, 2026
In public clouds, you can use the NetScaler appliance as a second-tier load balancer when the native load balancer is used as a 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. To monitor the health of the UDP application, public clouds recommend adding a TCP-based endpoint to your service. The endpoint reflects the health of the UDP application.
The NetScaler appliance supports external TCP-based health check for a UDP virtual server. This feature introduces a TCP listener on the VIP of the cache redirection virtual server and the configured port. The TCP listener reflects the status of the virtual server.

To enable external TCP health check for UDP virtual servers by using CLI

At the command prompt, type the following command to enable an external TCP health check with the tcpProbePort option:
add cr vserver <name> <serviceType> -tcpProbePort <tcpProbePort>  
Example:
add cr vserver Vserver-CR-1 HTTP -tcpProbePort 80

To enable external TCP health check for UDP virtual servers by using GUI

  1. Navigate to Traffic Management > Cache Redirection > Virtual Servers, and then create a virtual server.
  2. Click Add to create a virtual server.
  3. In the Basic Settings pane, add the port number in the TCP Probe Port field.
  4. Click OK.