Alam vs event vs trap in NMS, EMS

Event:

An event is an occurrence or detection of some condition in or around the network. An event is a distinct incident that occurs at a specific point in time. Examples of events include:

· Port status change

· Device reset

· Device becomes unreachable by the management station

An event can also result from:

· A fault that is an error, failure, or exceptional condition in the network. For example, when a device becomes unreachable, an unreachable event is triggered.

· A fault clearing. For example, when a device state changes from unreachable to reachable, a reachable event is triggered.

Alarm generated by NE and NMS:

· By receiving notification events and analyzing them; for example, syslog and traps.

· By automatically polling devices and discovering changes; for example, device unreachable.

Alarm:

An alarm is a NMS response to one or more related events. If an event is considered of high enough severity (critical, major, minor, or warning), NMS raises an alarm until the resulting condition no longer occurs.

One or more events can result in a single alarm being raised. An alarm is created in the following sequence:

1. A notification is triggered when a fault occurs in the network.

2. An event is created, based on the notification.

3. An alarm is created after verifying that there is no active alarm corresponding to this event.

Traps:

Traps are used when the Device needs to alert the Network Management software of an event without being polled. Traps ensure that the NMS gets information if an certain event occurs on the device that needs to be recorded without being Polled by the NMS first.

Managed network devices will have Trap MIBs with pre-defined conditions built into them. Its crucial that the Network management system has these MIBs compiled into them to receive any traps sent by the given device/s.

MIBs are number that identify certain characteristics or values of a device, but if the Network Management system does not have a certain MIB that the network device Trap is sending, there is no way to interpret what the MIB is and will not record the event.

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