How can I know when a monitored server goes down?

You can be notified when a monitored server goes down.

When IBM® Sterling Control Center Monitor is no longer in communication with a monitored server, it assumes the server has stopped and generates an event of type Server Status with a message ID of CCTR034E.
  1. To be alerted of this condition, create a rule that specifies the following parameter:
    Key Operator Value
    Message ID Matches CCTR034E
  2. Specify an action with a severity level that generates an alert (such as severity level 2).
    Tip: The IBM Sterling Control Center Monitor consoles also relate real-time information about server up or down status.