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Running Discovery and Extensive Monitoring version 1 (EM1) periodically

When you decide to run Discovery and EM1 periodically, pay attention to the following:

• For best Discovery and EM1 results, enable SNMP support on as many network devices as possible and preferably use a standard set of community names.
• If you decide not to draw your complete network in the Monitor one network maps, add at the least the backbone with its core routers and switches and enable EM1.
• If you are managing a WAN with relatively slow and/or expensive network links, do not specify additional IP ranges that are behind those slow lines!

To adjust the Discovery and EM1 settings:

1. Switch to Designer mode.
2. Select Options|Global configuration from the menu on the main window
3. Select the Discovery + EM1 tab
4. The "Discovery and Extensive Monitoring" window opens.
   
   
   
   The snapshot above shows the default settings. By default EM1 is enabled and Discovery is disabled.

If you have defined (additional) IP ranges and you want these ranges also being scanned periodically, check the Run discovery checkbox and define a time interval. The default scanning interval is 9 hours. Additional IP ranges are also scanned by EM1 if EM1 is enabled.

Note that if you want to make a one-time-only scan of one or more IP ranges in order to use the discovered nodes for building a new network map, leave the Run Discovery every checkbox unchecked! Go instead to the "Discovery / Discover IP nodes" window directly, define one or more ranges and run Discovery interactively.

We would like to remind you - perhaps unnecessarily – that if you leave the Run Discovery every checkbox unchecked and the Enable EM1 checkbox checked, EM1 will automatically scan the devices on the map every four hours. The time interval specified in the Discovery pane is not used by EM1!

If Discovery finds a new IP node, it tries to retrieve SNMP data from the node using the communities listed in the Communities to use listbox. The first six community strings in the list are system defaults that cannot be removed or modified.

Adding new communities to the list

1. Right-click anywhere in the Communities to use box and select Add a community.
2. The "Add a community" window opens.
3. Enter a community string into the Community box.
4. Press Add.

Removing communities from the list

1. Right-click the community string to remove in the Communities to use box and select Remove this community.

Defining EM1 Thresholds

• You can modify EM1 thresholds by pressing the Set EM1 thresholds button.

Modifying EM1 thresholds is not recommended! The default settings have been determined by extensive testing.

Discovery and Intrusion Detection systems

Note that, if Discovery is running, some intrusion detection systems may start sending alerts in order to inform the network manager that someone is trying to connect to an abnormally high number of hosts with an abnormally high number of different community names, which may indicate that a network attack is under course.