A host is down or unreachable, depending on its location in the network:
- down — the host is the first one it can not reach in the network.
- unreachable — the host is after the host described above.
The picture below shows how a network looks like from the monitor servers point of view.
As you can see everything starts with the OP5 Monitor server. If fw-01 is down, as shown in the picture above, all child hosts of fw-01 is considered as unreachable.
The example above shows that you can use parenting to exclude a lot of unnecessary alerts and notifications. This because you can tell OP5 Monitor not to send any notifications for a host that is unreachable. That means you will only get notification about fw-01 in this case, not the hosts "below" fw-01.