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ikkut23's avatar
Icon for Altostratus rankAltostratus
Sep 24, 2022

Pool active/standby


i was wondering if there is a way to create a pool with 2 servers active/standby with no preempt.

I try to explain better.


I have many Virtual Server, each of them has its own pool and servers

One of these pool has 2 servers: Server A and Server B

i would like to set server A as Active and Server B as Stanby, in case of fail for server A, Server B will become the active and server A unavailable(this can be achieved by PGA) .The problem for me seems to be when server A will be back available, i want Server B to still work as active and server A to join the pool as Standby.

Could you guys help in order to know which method should i use



5 Replies

  • xuwen's avatar
    Icon for Cumulonimbus rankCumulonimbus

    create pool_web has 2 pool members, enable priority group function, Server A priority is 10, Server B priority is 5, Less than 1 member
    VS enable dest_addr persist function

    • ikkut23's avatar
      Icon for Altostratus rankAltostratus

      Thank you xuwen , any idea how to accomplish that with something like an icall script , lets say change PGA when Server A will be down 



  • Hello, this is quite tricky, you might consider adding a member-specific monitor to memberA that cross-checks memberB and marks memberA down if node B has traffic. Of course this sould require careful tuning. 

  • You can achieve part of your requirement using priority group activation with destination persistence. 

    1. Server A goes down.

    2. Priority Group Activation kicks in and activates Server B to take traffic.

    3. Server A comes back.

    4. Due to Priority Group Activation Server A will start taking traffic as Server B will go inactive due to lower priority. So the persistent connections will stay on Server B, but all new connections will go to Server A. (Not sure of exact behavior, to be tested)

    OPTION - 2

    If you really want to keep Server B as active even when Server A is available, you can use a customized HTTP monitor with "Time Until Up" feature (for example, keep it down for 30 minutes) for Server A to keep it down for as long as you need to.

    OPTION - 3

    You need to find an external script or automation tool to monitor Server B status for active connections and change its Priority Group Acitvation priority to be more than that of Server A.

    OPTION - 4

    Trigger alert when Server A goes down so that you can manually login to the device and change the Priority Group Acitvation priority of Server B to be more than that of Server A.

    Try out the scenarios in lab enviroment and you should be able to select the one easiest and most suitable for you.

    Good Luck!


    Mohammed Mohsin

    • ikkut23's avatar
      Icon for Altostratus rankAltostratus

      Hi Mohammed ,


      thank you very much for your response , i`m more interested on option 3 

      any idea how to develop an solution with this option