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Reachability Logic in Action
Now that you're ve configured Shinken Enterprise with the proper parent/child relationships for your hosts, let's see what happen when problems arise. Assume that two hosts - Web and Router1 - go offline...
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When hosts change state (i.e. from UP to DOWN), the host reachability logic in Shinken Enterprise kicks in. The reachability logic will initiate parallel checks of the parents and children of whatever hosts change state. This allows Shinken Enterprise to quickly determine the current status of your network infrastructure when changes occur. During this additional check time, the notification for the web and router1 hosts are blocked because we don't know yet **WHO** is the root problem.
In this example, Shinken will Enterprise will determine that Web and Router1 are both in DOWN states because the "path" to those hosts is not being blocked (switch1 is still alive), and so **it will allow web and router1 notifications to be sent**.
Shinken will Enterprise will determine that all the hosts "beneath" Router1 are all in an UNREACHABLE state because Shinken canEnterprisecan't reach them. Router1 is DOWN and is blocking the path to those other hosts. Those hosts might be running fine, or they might be offline - Shinken doesnEnterprise doesn't know because it can't reach them. Hence Shinken considers Enterprise considers them to be UNREACHABLE instead of DOWN, and won't send notifications about them. Such hosts and services beneath router1 are the impacts of the root problem "router1"
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One important point to remember is Shinken only Enterprise only notifies about root problems. If we allow it to notify for root problems AND impacts you will receive too many notifications to quickly find and solve the root problems. That's why Shinken will Enterprise will notify contacts about DOWN hosts, but not for UNREACHABLE ones.
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You will not be notified about all critical or warning errors on a down or unreachable host, because such service states are the impacts of the host root problem. You don't have to configure anything, Shinken Enterprise will suppress cancel these useless notifications automatically.
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