Device filters
Use prediscovery filters to increase the efficiency of discovery.
After you have defined the scope of your discovery using the Scope tab, it is possible to restrict the scope using filters. For example, you might want to maintain the scope zones that you defined earlier but restrict the scope based on location (for example, New York hardware only) or based on hardware supplier (for example, Cisco devices only).
You can filter out devices based on a variety of criteria, including location, technology, and manufacturer.
By default, the discovery filters do not filter out the Network Manager host because it usually also serves as the polling station for root cause analysis. For root cause analysis to work correctly, the polling station, and hence the Network Manager host machine, must be part of the topology.
If you do need to filter out the Network Manager host, then you need to modify the following stitchers and remove the sections of code, indicated by comments, that prevent the Network Manager host from being filtered. The stitchers are DetectionFilter.stch and InstantiationFilter.stch.
Prediscovery filter
You might want to apply this filter to sensitive devices that you do not want to poll. A device might be considered sensitive because there is a security risk involved in polling the device, or because polling might cause the device to overload.
Prediscovery filters prevent the discovery from retrieving detailed data or connectivity data from the device and prevent discovered devices from being polled for connectivity information. Only devices matching the prediscovery filter are fully discovered. If no prediscovery filter is defined, then all devices within the scope are discovered.
Details.returns OQL table in the discovery (Disco)
service, so you can use fields other than IP addresses, such as m_ObjectId (equivalent to
sysObjectId). A device must pass all filters to be discovered.You can configure the filter condition to test against any of the columns in the Details.returns table. But, you might need to use the IP address (m_UniqueAddress) as the basis for the filter to restrict the detection of a particular device. If the device does not grant SNMP access to the Details agent, the Details agent might not be able to retrieve MIB variables such as the Object ID. However, you are guaranteed the return of at least the IP address when the device is detected.
You can define multiple prediscovery filters. Filters are combined automatically using a Boolean AND expression. All criteria defined in all filters must be matched.