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jamesdris's avatar
jamesdris
Icon for Nimbostratus rankNimbostratus
Mar 19, 2019

F5 DNS sync groups, datacenters and prober pools

I have a few questions - 1 - Can we have prober pools in a global availability mode? If yes does it mean when the primary listener is down the servers will be polled using the secondary prober on the configuration? 2 - If no prober pool is attached to a server or a dataceneter, which of the DNS servers in sync group poll the servers configured? 3 - In datacenter/server where no prober pool is configured, if one of the DNS servers marks an LTM virtual down and while the other marks it online, which status is finally attached to the DNS query result?

 

application delivery
BIG-IP DNS
f5 dns sync group
prober pool

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  • Rico's avatar
    Rico
    Icon for Cirrus rankCirrus
    Mar 19, 2019
    1. Yes, global availability can be configured and it just means it will use the first available member of the pool. You can see that in the Create a Prober Pool section of this article
    2. If no prober pool is configured, the BIG-IP DNS devices negotiate amongst themselves which DNS device is responsible for which server.
    3. If there is a discrepancy in DNS devices marking a device as up, it will choose the health monitor data from the BIG-IP DNS device assigned to that server.

    If you have any more questions, I am sure I can help

     

  • Rico_368208's avatar
    Rico_368208
    Icon for Nimbostratus rankNimbostratus
    Mar 19, 2019
    1. Yes, global availability can be configured and it just means it will use the first available member of the pool. You can see that in the Create a Prober Pool section of this article
    2. If no prober pool is configured, the BIG-IP DNS devices negotiate amongst themselves which DNS device is responsible for which server.
    3. If there is a discrepancy in DNS devices marking a device as up, it will choose the health monitor data from the BIG-IP DNS device assigned to that server.

    If you have any more questions, I am sure I can help

     

    • jamesdris's avatar
      jamesdris
      Icon for Nimbostratus rankNimbostratus
      Mar 20, 2019

      so, imagine GTM1 is in DC1 and GTM2 is in DC2, and server1 is assigned GTM1 as a prober. If GTM1 marks server1 up while GTM2 marks it down will the server in effect be marked up or down?

       

      also, what would happen if GTM1 is not able to reach the server1(but GTM1 is actually online) and marks it down while communication between GTM1 and GTM2 works well?

       

    • Rico's avatar
      Rico
      Icon for Cirrus rankCirrus
      Mar 20, 2019

      In your first situation server1 would be marked as up because the health statistics would come from GTM1. In your second scenario, as long as the GTM1 sees the server as down, it will be marked down. The GTM devices will choose a device in the same datacenter as the device that it is trying to monitor. Even if that healthcheck is incorrect, the monitor status from the device in the same datacenter is what will be used.

       

    • Rico_368208's avatar
      Rico_368208
      Icon for Nimbostratus rankNimbostratus
      Mar 20, 2019

      In your first situation server1 would be marked as up because the health statistics would come from GTM1. In your second scenario, as long as the GTM1 sees the server as down, it will be marked down. The GTM devices will choose a device in the same datacenter as the device that it is trying to monitor. Even if that healthcheck is incorrect, the monitor status from the device in the same datacenter is what will be used.