System Supervision - Using SNMP for monitoring & notification of fault/clear conditions

What is SNMP?

Simple Network Management Protocol (SNMP) is an Internet-standard protocol for managing devices on IP networks. Devices that typically support SNMP include routers, switches, servers, workstations, printers, modem racks, and more. It is used mostly in network management systems to monitor network-attached devices for conditions that warrant administrative attention. 

In typical SNMP uses, one or more administrative computers, called managers, have the task of monitoring or managing a group of hosts or devices on a computer network. Each managed system executes, at all times, a software component called an agent which reports information via SNMP to the manager.

Essentially, SNMP agents expose management data on the managed systems as variables. The protocol also permits active management tasks, such as modifying and applying a new configuration through remote modification of these variables if supported by the variables.

Variables accessible via SNMP are organized in hierarchies. These hierarchies, and other metadata (such as the type and description of the variables), are described by a file called the MIB (Management Information Base) file.


How can I view faults using SNMP?

First, obtain the IED MIB file which describes the SNMP variables/properties that can be queried for current system faults. Next, load the IED MIB file in a SNMP aware network management software (like HP OpenView, for example). This allows the management software to display the SNMP variables/properties supported on the vACS unit in a tree like hierarchy. Navigate the object tree to the ied node (having Object ID Drill down further to nodes software, services, and finally to faultLoggerService. This node exposes three SNMP variables for querying faults. The totalFaults variable can be queried for the total number of faults that are known by the vACS unit. The lastFault node displays the fault description, time of first and last occurrences, and other technical details about the fault condition. The currentFaultTable variable displays in a tabular manner the same details as the lastFault variable for all known faults in the system. 

Most modern network management software provides user friendly mechanisms to view (via SNMP Get request) SNMP variables. Typically, one right clicks on a SNMP property and selects “Get” or “View as Table”  from a popup menu or the toolbar. Please consult you network management software documentation or help file for details on this step.


What are SNMP Traps?

SNMP Traps are unsolicited message sent from an SNMP aware device to the management station/software for notification of significant events. 

The idea behind trap-directed notification is that if a management software is responsible for a large number of devices, and each device has a large number of objects, it is impractical for the manager to poll or request information from every object on every device. The solution is for each agent on the managed device to notify the manager without solicitation. It does this by sending a message known as a trap.

After the manager receives the event, the manager displays it and can choose to take an action based on the event. For instance, the manager can poll the agent directly, or poll other associated device agents to get a better understanding of the event. 

Trap-directed notification can result in substantial savings of network and agent resources by eliminating the need for frivolous SNMP requests. 


How can I receive SNMP Traps?

The vACS unit must be setup to generate SNMP Traps for fault and clear incidents. The sub-unit responsible for monitoring devices is a windows service running inside the vACS unit called the System Supervision Service. Verify that the service is configured to generate SNMP Traps. This process is described in detail in the Zendesk article titled “IED System Supervision – Post Install Setup”.

The next step is to enter the IP Address of the computer that is running the network management software, i.e., the receiver of the SNMP Traps. Please refer to the section titled “SNMP Endpoints” of Chapter 18 in the document attached to the Zendesk article titled “GlobalCom System Management Centre (SMC) User Manual” for complete and updated steps.

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