Open source Nagios is an enterprise-class tool, used for monitoring networks, which runs on Linux and Unix. By running periodic checks on user-specified resources and services, Nagios ensures faster fixes for network issues.
Chapter 7 -- "Testing Local Resources" -- of Nagios: System and Network Monitoring details the various plug-ins needed to work with Nagios and how to test them over a local network since some lack their own network protocol.
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