We need to send alert shows if hosts status change from down to up please help me how we can do this
Generally, like this:
index=YouShouldAlwaysSpecifyAnIndex sourcetype=AndSourcetypeToo
| dedup host status
| search status="up"
Save this as an alert with When event count
and Is greater than 0
Provide examples from the events/logs that you are planning to leverage.
Refer to the following answer for several ways you can do it including one where you can check for Last Phone Home time for each host using REST service call: https://answers.splunk.com/answers/525926/how-do-we-determine-whether-a-forwarder-phoned-hom.html