Nagios Core - Determining Status and Reachability of Network Hosts

Nagios is able to determine whether the hosts you're monitoring are in a DOWN or UNREACHABLE state. These are very different (although related) states and can help you quickly determine the root cause of network problems. This documentation explains how the reachability logic works to distinguish between these two states.

Documentation - Determining Status and Reachability of Network Hosts

Final Thoughts

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