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G_Q_245664's avatar
G_Q_245664
Icon for Nimbostratus rankNimbostratus
Feb 25, 2016

LTM - Setting dependancy between monitors

Not sure if this is even possible but here is the scenario:

 

I have a pool of IIS servers configured as members of two sets of pools based on TCP ports configured in IIS. (I was told that you need to create a separate VS per port you want to load balance).

 

So... per the web devs, port 10000 is for responding to TCP traffic (restful web calls, etc.). Port 10001 is responding to http requests.

 

Virtual Server 1 (TCP port 10000) Virtual Server 2 (TCP port 10001)

 

Pool 10000 (has Servers 1-3/port 10000 as members) Pool 10001 (has Servers 1-3/port 10001 as members)

 

I have an http monitor which is working correctly which monitors pool 10001 for successful get responses and works as expected. Disable web service on Server1, the Pool 10001 shows Server1 as down.

 

My problem is that Pool 10000 shows Server 1 as still being up as its just using the standard icmp monitor, thus traffic is still being passed to that server.

 

Is it possible to set a dependency on the icmp monitor to the http monitor associated with pool 10001?

 

So if the web server is down on a server, no traffic is sent to that server regardless if its still responding to ping? If it's not responding to ping, then obviously the web monitor would be down as well.

 

Sorry, really new to LTM concepts so still learning this awesome system.

 

Thanks,

 

George

 

application delivery
application monitors
iRules
LTM
  • G_Q_245664's avatar
    G_Q_245664
    Icon for Nimbostratus rankNimbostratus
    Feb 25, 2016
    Pool Member object. Basically, if the web service goes down on Server X, I don't want to direct any requests to that server regardless of if it responds successfully to ICMP.
  • Kai_Wilke's avatar
    Kai_Wilke
    Icon for MVP rankMVP
    Feb 25, 2016

    Hi George,

     

    you could attach a TCP:10000 and HTTP:10001 monitor to both pools (by specifying "Alias Service Ports") and set the monitor requirment to all monitors. On this way the pool members would become active if both services are running.

     

    And just keep the default ICMP-Monitors on the node-level without any changes...

     

    Cheers, Kai

     

    • David_M's avatar
      David_M
      Icon for Cirrostratus rankCirrostratus
      Jun 25, 2019

      Meaning he should attach http monitor on TCP:10001 pool and in the alias address and port add the other pool member IP:10000.

       

      But why does he need to do it on both?

      • Kai_Wilke's avatar
        Kai_Wilke
        Icon for MVP rankMVP
        Jun 27, 2019

        Hi DavidMas,

         

        yes...

         

        If you don't specify an alias address and port the monitor will start to probe the individual Pool Member IP/Ports.

        If you specify an alias address and/or port the monitor will probe a service via a given IP/Port (probably outside of your Pool), but will have an impact on the availability of the Pool where the Monitor is attached.

         

        Cheers, Kai

         

  • Greg_Labelle's avatar
    Greg_Labelle
    Icon for Nimbostratus rankNimbostratus
    Feb 25, 2016

    Each pool is independently controlled based on the health monitor attached. Unless the server in question does not respond to a ping, the icmp monitor would report port 10000 as available.

     

    You have a few options:

     

     

    1. For maintenance, disable the node on the F5 which will offline it in all pools associated

     

    or

     

    2. Implement a TCP or script monitor that can accurately assess the status of the TCP service listening on 10000

     

    or

     

    3. Implement a HTTP monitor with an alias port of 10001 that will mark the TCP service down if the HTTP service is unavailable.

    Good luck!