
[[filter-components]]
= OpenNMS components that use filters
:description: Get a list of the OpenNMS {page-component-title} components that use filters/rules: notfifd, collectd, pollerd, threshd, and the web UI.

== notifd

Notification rules control whether a received event triggers a notification.
Each event is tested against the rules in notifications.xml looking for a match.
When a match is found, the corresponding notification is sent.
The default for most notifications is `IPADDR IPLIKE *.*.*.*`; however, you may use any valid rule.

For an exclusive filter, use `!(IPADDR IPLIKE 169.254.*.*)`.
This allows you to be very granular when defining what to alert on.

== collectd

Controls which IP interfaces to include in a collection package.
Evaluated at startup.

== pollerd
Controls which IP interfaces to include in a polling package.
Evaluated at startup.

== threshd
Controls which IP interfaces to include in a thresholding package.
Evaluated at startup.

== WebUI
The webUI uses filters to validate rules when configuring notifications.
This ensures that the rule will be syntactically correct, and allows the administrator to preview the list of matching interfaces before finalizing the notification.

You can also use filters with rules to configure path outages to select a list of nodes that lie behind the specified outage path.
You can preview this list before finalizing the configuration.