Why does the Netprobe log show repeating errors like "Cannot get device settings: Invalid argument"?

In older versions of Netprobe or Linux kernel, the Network plugin relies on OS commands to retrieve information for Duplex and Link information.

If it is not configured properly, the following errors may be seen which are output from "ethtool" command.

Cannot get device settings: Operation not permitted 
Cannot get wake-on-lan settings: Operation not permitted 
Cannot get message level: Operation not permitted 
Cannot get link status: Operation not permitted

Cannot get device settings: Invalid argument
Cannot get wake-on-lan settings: Invalid argument
Cannot get message level: Invalid argument
Cannot get link status: Invalid argument