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Health Monitors


rev.dennis

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So Health Monitors are a big deal to ensure your pool members are up and working.  Obviously a health monitor tells whether a pool member is up or down and when its down the pool won’t send any traffic to that pool member.

Now you can assign health monitors two different ways.  The right way and the wrong way but sometimes the wrong way is the right way but not the majority of the time…  its more of a custom thing.  Let me explain further

Example of a pool health monitor

ltm pool /Integration/pool.cs-inspire-batch-cap.int.thezahcom.ssh {
    load-balancing-mode least-connections-member
    members {
        /Integration/10.45.89.242:22 {
            address 10.45.89.242
            session monitor-enabled
            state up
        }
        /Integration/10.45.89.243:22 {
            address 10.45.89.243
            session monitor-enabled
            state up
        }
    }
    monitor monitor_22
    partition Integration
}

Here is an example of the “custom” or incorrect way

ltm pool /Integration/pool.iwarranty-iwnacap.int.thezah.com.22 {
    members {
        /Integration/sat1svmap140:22 {
            address 10.45.88.103
            monitor tcp
            session monitor-enabled
            state down
        }
        /Integration/sat1svmap141:22 {
            address 10.45.88.106
            monitor tcp
            session monitor-enabled
            state down
        }
        /Integration/sat1svmap142:22 {
            address 10.45.88.109
            monitor tcp
            session monitor-enabled
            state down
        }
        /Integration/sat1svmap143:22 {
            address 10.45.88.112
            monitor tcp
            session monitor-enabled
            state down
        }
    }
    monitor monitor_22
    partition Integration
} 

Can you see the difference?  Unlike the first one, this has a monitor set at the pool level and then they trump that pool monitor with a health monitor set on each pool member.  In this case you never ever want a tcp health monitor on ssh box…  it will cause lots and lots of errors.

So to remove those monitors assigned to each pool member you would run a command like this

tmsh modify ltm pool /Integration/pool.iwarranty-iwnacap.int.thezah.com.22 members modify { /Integration/sat1svmap140:22 /Integration/sat1svmap141:22 /Integration/sat1svmap142:22 /Integration/sat1svmap143:22 { monitor default } }

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