GTM: avoiding flapping DNS answers with RTT method
I am in the need to understand how GTM metrics work for GTM LDNS probes.
1) how they can be logged the decision? I am using 11.2 but moving fast to 11.4.1.. :)
2) Lets make an example. if our GTM chooses a VIP in USA for 100 consecutive times because the RTT is lower going to this USA VIP and then for 1 time it gets a better value - for whatever reason - to go to another VIP, for example to Australia, will it be considered valid the last value which differs from the original 100 previous time? is there cache variation value that can be configured to avoid this flapping choices? (We had this choice in Cisco GSS).
3) how long is the non-optimizes Australian value kept in cache until a new value is reconsidered? It is the Inactive timeout of 28 days?
The only solution I could see in your situation is to break your single pool into three pools, and either stick with RTT and enable persistence at the wide IP, or switch to topology. Either one should get you some more consistency.