User's Manual

276 CHAPTER 7: MONITORING THE NETWORK
For details on how to start monitoring an unmonitored device or link, or
to stop monitoring a monitored device or link, see “
Starting and Stopping
Monitoring” on page 293.
For more information on event severities see “Event Severities” on
page 321
Monitoring State and the Grouped View
When you are viewing the devices in your network grouped by subnet,
3Com Network Director propagates the monitoring states of devices,
links and submaps up the submap hierarchy.Each submap is colored to
indicate the most critical monitoring state of the devices, links or
submaps that it contains.
For example, if a subnet contains two devices, one of which has a red
monitoring state and one of which has a yellow monitoring state, the
subnet will be colored red. If the event causing the red device's
monitoring state is subsequently resolved, the subnet will change to be
colored yellow, as this is now the most critical monitoring state contained
within the subnet.
When determining the monitoring state of a submap, 3Com Network
Director ignores any map items or links that are visible at a higher level in
the hierarchy than the submap itself.For example, the monitoring state of
a router will not affect the monitoring state of the subnets that it is
present on, as the router is visible in the top-level map, which is the
highest level in the hierarchy.
Monitoring
Techniques
3Com Network Director uses various techniques to monitor the state of
devices and links within your network.The techniques used for a
particular monitor depend upon the feature that is being monitored, and
can be broadly broken down into active and passive monitoring:
Active Monitoring: Active monitoring works by 3Com Network
Director polling, and possibly retrieving data from, a device on a regular
basis.Once the device has been polled, or once the data has been
retrieved from the device, 3Com Network Director can analyze the results
to determine the state of the device.There are various mechanisms used
for active monitoring, including sending IP pings, retrieving data from
SNMP MIBs, and directly checking for service availability.