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Thanks to philh, Mark S., Rao, and Mark for their contributions.
 
Looking for assistance determining where my use of the above code may have gone wrong.
 
Steps taken:
 
A) Within /shared/lib, created "perl5" directory with default permissions.
 
B) Per this page: https://devcentral.f5.com/s/articles/ntp-monitor-for-11x-with-complete-instructions-999 Downloaded and extracted ntp.zip contents. TFTPed NTP.pm to /shared/lib/perl5 and saved it with 755 permissions.
 
C) Used the code above in a file named "ntp_mon."
 
D) Used the F5 File Management External Monitors section to upload "ntp_mon" as "MON_EXT_NTP."
 
E) Created a Monitor called "MON_NTP" that used "MON_EXT_NTP" as an external monitor.
 
F) Modified the Pool to use the "MON_NTP" monitor.
 
Results: Pool Members showed as red diamond down.
 
I did not use Arguments or Variables when creating the external monitor configuration as neither article mentioned the configuration of arguments or variables.
 
I just re-re-read one of the articles and noticed that it uses only the "default" IP and Port. I wonder what the author means by this. I presumed that the monitor would send an NTP request to the IP address of the Member over its IP and Port. I also assumed that the BIG-IP would be intelligent enough to use a static or floating self IP on the same subnet as Member in order to attempt to perform the NTP query.
 
Thanks for your input,
 
John