F5's UDP health check method
Theoretically speaking, the UDP health check method is that the client sends all the time, but regardless of whether the result is received or not, how does the F5 udp health check method determine the survival of the back-end server udp port? up.
packet capture analysis
Under normal circumstances, UDP detection, when the back-end service is normal, there is no abnormality in the back-end. When the back-end service port is unreachable, the udp detection will return an icmp exception packet.
Capture packets on the server side and perform port detection on the client side. The packet capture results are as follows:
The result is consistent with the packet capture display on F5. When the backend udp port is abnormal and there is a request to the backend service, the backend service will send an icmp “udp port radan-http unreachable” to inform the client that there is a problem with this port.
Therefore, for UDP services, no news is the best news.