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Using Network Load Balancer with TCP health check

Received Response
edited Apr 12, 2021 9:41PM in Oracle Cloud Infrastructure - General 12 comments


Looking for example of TCP health check with network load balancer


I have been exploring the new(er) Network Load Balancer service and am having difficulty preparing even a simple configuration using a TCP health check. While I have been successful with HTTP health checks I'm not yet able to pass a health check using TCP. Consider this example:

  • Create NLB with src/dest preservation disabled
  • Create Backend Set with dest preservation disabled and TCP health check to port 53
  • Create Backend that targets network-accessible DNS server listening on TCP 53

I've tried this simple example more than once but find my Backend never shows healthy. I can hit the backend directly on TCP/53 (using ncat or otherwise) and find the server responds. I am certain there are no missing Security Rules interfering. Also, I have enabled Subnet Logging and see traffic to/from the Backend but the NLS continues to report the Backend is "CRITICAL."

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