External monitors let you create custom scripts that contain specific logic that is not available in built-in BIG-IP monitors to monitor the health of pool members and nodes. An external monitor contains the following three components:

A BIG-IP monitor that references a script.
A script that contains logic to determine the health of a back-end server.
A command in the script, such as cURL or Netcat, that interacts with the back-end server.

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