Ipswitch WhatsUp Gold User Guide - Ipswitch Documentation Server

Ipswitch WhatsUp Gold User Guide
Example
In this example, a network segment has a group of devices, each with a dependency on
another for its connectivity. Each of these devices has a Ping monitor used to determine the
state of the device, denoted Ping (device). If Host A can be pinged from another network
segment, then it can be assumed that Router R, and Switch N are up and available, so to
operate separate ping monitors on these devices creates unneeded overhead as long as Host
A is up. However if Host A is powered down, or otherwise unreachable by the Ping monitor,
we must rely on the Ping (Switch N) and Ping (Router R) monitors to ensure that these devices
are up and accessible.
Adding a down dependency on Switch N to the Ping monitor on Host A, Down
Dependency: Host A (Ping Monitor), and a down dependency on Router R to the Ping
monitor on Switch N, Down Dependency: Switch N (Ping Monitor), creates a chain of
dependencies that will monitor the network segment and reduce the active monitors that
must operate on the segment when it is fully operational.
With these dependencies added, if Ping (Host A) should go into a down state, the down
dependency on Switch N will cause WhatsUp Gold to begin polling Switch N. If the polling of
Switch N is successful, it will continue to be polled until Host A is recovered. However if
Switch N is also unreachable and Ping (Switch N) goes into a down state, the down
dependency on Router R will cause WhatsUp Gold to begin polling Router R. When Ping
(Switch N) returns to an up state, Router R will no longer be polled. Likewise when Ping
(Host A) returns to an up state, Switch N will no longer be polled.
Down dependencies and the "assumed up" state
A down dependency on a device can lead to an "assumed up" state, where a monitor on the
dependent device indicates that it is up, regardless of its actual state.
This condition occurs when the dependent device is in an inactive state, and is able to
respond to an echo request from a ping of the device. Because of the down dependency, the
dependent device is not being polled and is "assumed up", yet the actual state of the
monitored service or process is unknown, and may have even failed.
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