F5 DNS external monitor

i'm using 2 F5 DNS units in a sync group . (version 12.1.2)

we have 2 datacenters (DC1 & DC2) . In each datacenter we deployed an F5 DNS .

hereunder is the config like it was created (I changed DNS names & IP's but nothing else) :

gtm datacenter /Common/DC1 {

   description "Datacenter DC1"

}

gtm datacenter /Common/DC2 {

   description "Datacenter DC2"

}

gtm prober-pool /Common/GTM-Probers-DC1 {

   members {

       /Common/unit-dc1 {

           order 0

       }

       /Common/unit-dc2 {

           order 1

       }

   }

}

gtm prober-pool /Common/GTM-Probers-DC2 {

   members {

       /Common/unit-dc1{

           order 1

       }

       /Common/unit-dc2 {

           order 0

       }

   }

}

gtm server /Common/DC1-Openshift-virtual-ip {

   addresses {

       10.100.100.100 {

           device-name /Common/DC1-Openshift-virtual-ip

       }

   }

   datacenter /Common/DC1

   prober-pool /Common/GTM-Probers-DC1

   product generic-host

   virtual-servers {

       testname.domain {

           destination 10.100.100.100:443

           monitor /Common/Test

       }

   }

}

gtm monitor external /Common/Test {

   defaults-from /Common/external

   destination *:*

   interval 30

   probe-timeout 5

   run /Common/https-sni-monitor-v1

   timeout 120

   user-defined HOST testname.domain

   user-defined RECV 200

   user-defined URI /checkService

}

so we are creating a generic host without monitor . ANd than define a virtual server on F5 DNS based on that host on port 443 .Monitor "Test" is associated with this vs , and this is an EAV monitior pointing to file "https-sni-monitor-v1" . Which is the file with script mentioned earlier here .

This script was uploaded as a file , via "System" - "File management" - "external monitor" as is normal procedure described by F5.

When monitor is enabled on host , we see host being put "down" after the monitoring interval .

however when doing an tcpdump , we do not see anything going out to IP address of the host where monitor is defined .