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Senthil_7991's avatar
Senthil_7991
Icon for Nimbostratus rankNimbostratus
Aug 17, 2017

When disabled POOL member - How servers are receiving traffic

Hi,

 

We recently disabled one of the pool member on F5 LTM, another POOL member is still on active, but customer on server side still receiving traffic from this disabled POOL.

 

how the application server is receiving traffic if the VIP pool is disabled?.

 

And I can see difference of "disabled" and "force offline" like below

 

When set to Disabled, a node or pool member continues to process persistent and active connections. It can accept new connections only if the connections belong to an existing persistence session.

 

When set to Forced Offline, a node or pool member allows existing connections to time out, but no new connections are allowed.

 

Can you please explain?

 

application delivery
LTM

3 Replies

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  • Samir_Jha_52506's avatar
    Samir_Jha_52506
    Icon for Noctilucent rankNoctilucent
    Aug 17, 2017

    Due to session persistence setting on VIP, F5 send session to disabled pool member. It can accept new connections only if the connections belong to an existing persistence session. in that case you can make pool member force offline to avoid any issue.

     

    • Senthil_7991's avatar
      Senthil_7991
      Icon for Nimbostratus rankNimbostratus
      Aug 17, 2017

      Thanks for your update

       

      Understood,but our LTM setup is very simple,there is no persistence setting with this VIP.

       

      This is pure http ( port 80) settings running with two POOL members.

       

  • Stanislas_Piro2's avatar
    Stanislas_Piro2
    Icon for Cumulonimbus rankCumulonimbus
    Aug 17, 2017

    Hi,

    When you want to disable pool member for a scheduled operation, you can disable it several hours / minutes before operation.

    In this case:

    • every clients already connected are still connecting to the same server preventing session break. --> persistence bypass LB reselect.
    • every unknown client are not balanced to disable members.

    when operation starts, the number of clients on disabled members is less than active members. This is the expected behavior for most of customers.

    If you want to disable and force LB reselect for persistent connections, you can use 

    force offline

    disable
    and 
    Force offline
    actions don't delete existing connections.