When I telnet to vip with the specific port number. The "show flows" only can see it retains for 5 minutes. But I still see the connection is established on the servers. Is this someting relating the application software problem ? Because I have other application software, which works very similiar . When the connection is not displating in the "show flows", Is this meaning the connection dropping ? Please advise. Thanks in advance.
I'll try to keep it simple.
A flow is describes by a FCB (Flow Control Block).
The 'show flow' commands describe the info inside the FCBs
When a flow is idle for a predefine period of time (like 16 seconds for TCP), the
FCB is marked as reusable.
So at any given time the FCB info can be erased and replaced with new info.
The CSS can still use the FCB marked as reusable until its content is erased.
So, your connection could still be alive but the FCB has been marked to be reused and therefore you will end up losing the connection.
The 'show flow' only display the FCB that have not been marked as reusable.
The solution would be to increase the frequency of your heartbeat or use one of the command to increase the timeout on the CSS.