Cisco Catalyst 2960 Series, Configuration Manual

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• If you want to write EEM policies using the command-line interface (CLI) commands, you should be
familiar with the
“ Writing Embedded Event Manager Policies Using the Cisco IOS CLI ” module.
Information About Writing Embedded Event Manager Policies Using Tcl
EEM Policies
EEM offers the ability to monitor events and take informational or corrective action when the monitored
events occur or reach a threshold. An EEM policy is an entity that defines an event and the actions to be taken
when that event occurs. There are two types of EEM policies: an applet or a script. An applet is a simple form
of policy that is defined within the command-line interface (CLI) configuration. A script is a form of policy
that is written in Tool Command Language (Tcl).
EEM Applet
An EEM applet is a concise method for defining event screening criteria and the actions to be taken when
that event occurs. In EEM applet configuration mode, three types of configuration statements are supported.
The event commands are used to specify the event criteria to trigger the applet to run, the action commands
are used to specify an action to perform when the EEM applet is triggered, and the
set command is used to
set the value of an EEM applet variable. Currently only the _exit_status variable is supported for the
set
command.
Only one event configuration command is allowed within an applet configuration. When applet configuration
submode is exited and no event command is present, a warning is displayed stating that no event is associated
with the applet. If no event is specified, the applet is not considered registered. When no action is associated
with the applet, events are still triggered but no actions are performed. Multiple action configuration commands
are allowed within an applet configuration. Use the
show event manager policy registered command to
display a list of registered applets.
Before modifying an EEM applet, be aware that the existing applet is not replaced until you exit applet
configuration mode. While you are in applet configuration mode modifying the applet, the existing applet
may be executing. It is safe to modify the applet without unregistering it, because changes are written to a
temporary file. When you exit applet configuration mode, the old applet is unregistered and the new version
is registered.
Action configuration commands within an applet are uniquely identified using the label argument, which can
be any string value. Actions are sorted within an applet in ascending alphanumeric key sequence using the
label argument as the sort key, and they are run using this sequence. The same label argument can be used in
different applets; the labels must be unique only within one applet.
The Embedded Event Manager schedules and runs policies on the basis of an event specification that is
contained within the policy itself. When applet configuration mode is exited, EEM examines the event and
action commands that are entered and registers the applet to be run when a specified event occurs.
For more details about writing EEM policies using the Cisco IOS CLI, see the
“
Writing Embedded Event
Manager Policies Using the Cisco IOS CLI ” module.
EEM Script
All Embedded Event Manager scripts are written in Tcl. Tcl is a string-based command language that is
interpreted at run time. The version of Tcl supported is Tcl version 8.3.4 plus added script support. Scripts
are defined using an ASCII editor on another device, not on the networking device. The script is then copied
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
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Information About Writing Embedded Event Manager Policies Using Tcl