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SNMPc based Network Management Systems

A typical SNMP implementation includes three components:

  • Managed device
  • SNMP agent
  • Network management system (NMS)

A managed device is any device on a network, also known as a network element, that is managed by the network management system. Routers and switches are common examples of managed devices. The SNMP agent is the SNMP process that resides on the managed device and communicates with the network management system. The NMS is a combination of hardware and software that is used to monitor and administer a network.

The SNMP data is stored in a highly-structured, hierarchical format known as a management information base (MIB). The MIB structure is based on a tree structure, which defines a grouping of objects into related sets. Each object in the MIB is associated with an object identifier (OID), which names the object. The "leaf" in the tree structure is the actual managed object instance, which represents a resource, event, or activity that occurs in your network device.

The SNMP agent exchanges network management information with SNMP manager software running

on an NMS, or host. The agent responds to requests for information and actions from the manager. The agent also controls access to the agent's MIB, the collection of objects that can be viewed or changed by the SNMP manager.

The SNMP manager collects information about network connectivity, activity, and events by polling managed devices. Communication between the agent and the manager occurs in one of the following forms:

  • Get, GetBulk, and GetNext requests--The manager requests information from the agent. The agent returns the information in a Get response message.
  • Set requests--The manager changes the value of a MIB object controlled by the agent. The agent indicates status in a Set response message.
  • Traps notification--The agent sends traps to notify the manager of significant events that occur on the network device.

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