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    SNMP Server Event Manager Overview

    The SNMP server event manager works in conjunction with the Event MIB (RFC 2981). The purpose of this application is to allow many management functions (for example, fault detection, configuration management, accounting management, and performance management). These functions are traditionally performed by the network management station. However, by using the SNMP server event manager, you can distribute some of these functions to E Series routers and automate them.

    This section describes the following:

    Event MIB Purpose

    The rapid growth of networks has made it impractical to directly manage networks from a single network management station (NMS). This brought about a need for a model that both automated and distributed event management. The goal was to allow devices to monitor themselves and other devices, and to take action under certain conditions.

    The Event MIB (RFC 2981) defines a method for creating trigger conditions, testing those conditions, and determining which action to take when a trigger meets those conditions.

    The Event MIB allows you to define test conditions for object integers that are accessible in the agent, making it possible to monitor any aspect of a device without defining specific notifications and complicating the agent definition. In this model, because devices have the ability to monitor themselves or other devices, the processing is distributed throughout the network. Also, sending the information only to the NMS that uses an event model reduces both network overhead and processing drain on the NMS.

    Event MIB Structure

    The Event MIB has three major parts: the trigger table, the objects table, and the event table. These tables also contain subordinate MIB tables that contain more detailed information about the trigger tests.

    This section describes the following:

    Trigger Table

    The trigger table (mteTriggerTable) lists any currently-defined trigger conditions. Triggers fall into three categories—existence, Boolean, and threshold.

    An existence trigger tests for the existence of a MIB object instance; you can specify that the trigger occur by either the appearance, disappearance, or change in value of a MIB instance.

    A Boolean trigger tests whether the value of a MIB object (base syntax integer) is equal, unequal, greater than, less than, less than or equal to, or greater than or equal to some defined value.

    A threshold trigger verifies a MIB object (base syntax integer) in relation to either a rising threshold value, falling threshold value, or both.

    You can configure both Boolean and threshold tests to trigger on an absolute value or a delta value over a determined polling interval.

    Subordinate MIB tables exist within the trigger section of each type of trigger test. In other words, each type of trigger (existence, threshold, and Boolean) contains a table that stores added information about that type of trigger test.

    For example, a trigger entry of a specific type of test in the mteTriggerTable creates a linked entry in the appropriate subtable. In turn, this subtable contains more specific information about the specific test.

    A delta table also exists within the trigger tables. This table stores information about any delta values based on any Boolean and threshold triggers. The delta table stores a MIB object that indicates whether any discontinuities occurred for any delta trigger (for example, a router reset).

    Note: When determining discontinuity, the MIB object must be a time-based counter or number. When a polling interval expires and the event agent (router) needs to perform a delta calculation, it first checks the discontinuity MIB object for that trigger. If a discontinuity occurs, the agent does not perform the test for that trigger until the next polling interval.

    Objects Table

    The objects table (mteObjectsTable) defines objects that you want to add to event messages. In other words, you can create a list of user-specified objects and bind them to a trigger event. This can provide a snapshot of other values on a router when the trigger occurs. You can bind objects to a specific trigger, a type of test (for example, existence or Boolean tests), or a type of event (for example, rising or falling events).

    Note: This release does not support the objects table.

    Event Table

    The event table (mteEventTable) defines what action you want the device to take when a trigger occurs. This action can be in the form of a notification, setting a specified MIB object, or both. The results of these actions are controlled within two subordinate MIB tables—notification and set.

    Notifications (mteNotifications), or traps, define what the router sends when an event occurs. These traps include the following:

    • When a Boolean or existence trigger occurs, the router sends an mteTriggerFired trap.
    • When a rising threshold trigger occurs, the router sends an mteTriggerRising trap.
    • When a falling threshold trigger occurs, the router sends an mteTriggerFalling trap.
    • If a trigger fails to complete a test for any reason, the router sends a global mteTriggerFailure trap.
    • If an event fails to set, the router sends an mteEventSetFailure trap.

    Sets define certain modifications to other MIB objects based on a particular event.

    Published: 2014-08-12