# 3 Other event sources

#### Discovery events

Zabbix periodically scans the IP ranges defined in network discovery
rules. Frequency of the check is configurable for each rule
individually. Once a host or a service is discovered, a discovery event
(or several events) are generated.

Zabbix generates the following events:

|Event|When generated|
|-----|--------------|
|Service Up|Every time Zabbix detects active service.|
|Service Down|Every time Zabbix cannot detect service.|
|Host Up|If at least one of the services is UP for the IP.|
|Host Down|If all services are not responding.|
|Service Discovered|If the service is back after downtime or discovered for the first time.|
|Service Lost|If the service is lost after being up.|
|Host Discovered|If host is back after downtime or discovered for the first time.|
|Host Lost|If host is lost after being up.|

#### Active agent auto-discovery events

Active agent auto-registration creates events in Zabbix.

If configured, active agent auto-registration event is created when a
previously unknown active agent asks for checks or if the host metadata
has changed. The server adds a new auto-registered host, using the
received IP address and port of the agent.

For more information, see the [active agent
auto-registration](/fr/manual/discovery/auto_registration) page.

#### Internal events

Internal events happen when:

-   an item changes state from 'normal' to 'unsupported'
-   an item changes state from 'unsupported' to 'normal'
-   a low-level discovery rule changes state from 'normal' to
    'unsupported'
-   a low-level discovery rule changes state from 'unsupported' to
    'normal'
-   a trigger changes state from 'normal' to 'unknown'
-   a trigger changes state from 'unknown' to 'normal'

Internal events are supported since Zabbix 2.2. The aim of introducing
internal events is to allow users to be notified when any internal event
takes place, for example, an item becomes unsupported and stops
gathering data.