The Event Handling System (EHS) is a tool that enables operator-defined behavior to be configured on the 7705 SAR. The operator can define a CLI script that the router executes in response to a log event. The event is referred to as the trigger, where the trigger can be all or part of any event message. Regular expression (regexp) matching can be done on various fields in the log event to give flexibility in the trigger definition.
EHS gives operators the flexibility to configure the 7705 SAR to take actions based on specific events that cannot be done by protocols or services. For example, event-triggered actions can:
help with network convergence in response to a specific event
provide automatic exception handling upon detection of a specific problem
EHS objects are used to tie together trigger events (typically log events that match some configurable criteria) and a set of actions to perform (typically one or more CLI scripts).
EHS, along with CRON, makes use of the script-control functions for scripts. Any command available in the CLI can be executed in a script as the result of an event handler being triggered, except for commands that require interaction (for example, a y/n prompt for admin reboot without the now keyword, or commands that require a password). A script will error out if it encounters a command that requests input.
Figure: EHS Object Relationships shows the relationships between the different configurable objects used by EHS (and CRON).
