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afreudenr's avatar
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Jul 05, 2019

Pool member with sporadically listening service

We have following setup: a virtual server listening on port 80/http. Behind it is a pool member, which by default does not listen to anything. Only on manual intervention it runs acmetool (for creati...
  • Heino's avatar
    Jul 05, 2019

    I recommend looking at how fast your monitor is configured to be (un)available. I recommend tcp_half_open (it's faster).

    A very agressive monitor could be configured:

    Interval: 1

    Up interval: Disabled (it'll be online as soon as a succesful reply is received)

    Time Until Up: 0

    Time out: (however long you want the service to be available even when there's no successful response)

    Manual resume: No


    Additionally; you could add an alias service port. If the pool member is but the health monitor is to check 4402, you could specifiy 4402 in your monitor.


    if an active pool member starts to listen on a port - how fast is F5 expected to connect to it

    However fast your monitor interval + monitor up time + pool slow ramp combination is

    Slow Ramp shouldn't prevent traffic as the intention described shouldn't generate too much of it... but you never know.


    Possible troubleshooting:

    Verify that you haven't configured a connection limit


    There's a nice little tool called tcping (for windows). In cmd/powershell try running it before starting the service. Then you can see how quickly the vIP is online.

    .\tcping.exe -t 4402


    The mcpd process reports in your ltm log when it sees them member back online.