Simple Network Management Protocol (SNMP) is a set of protocols for network management and monitoring. These protocols are supported by many typical network devices such as routers, hubs, bridges, switches, servers, workstations, printers, modem racks and other network components and devices. Supported devices are all network-attached items that must be monitored to detect conditions. These conditions must be addressed for proper, appropriate and ongoing network administration. SNMP standards include an application layer protocol, a set of data objects and a methodology for storing, manipulating and using data objects in a database schema.
The SNMP protocol is included in the application layer of TCP/IP as defined by the Internet Engineering Task Force (IETF).
Typically, the Simple Network Management Protocol uses one or several administrative computers, called managers, which oversee groups of networked computers and associated devices. A constantly running software program, called an agent, feeds information to the managers by way of SNMP. The agents create variables out of the data and organize them into hierarchies. The hierarchies, along with other metadata, may be types and descriptions of the variables and are described by management information bases - hierarchical virtual databases of network objects.
Three key components of a network managed by SNMP are the managed devices (routers, servers, switches, etc.), software agents, and a network management system. There may be more than one NMS on a given managed network.
SNMP uses 7 protocol data units: GetRequest, SetRequest, GetNextRequest, GetBulkRequest, Response, Trap and InformRequest. The PDUs enable requests for specific data in the form of variables from the hierarchical virtual databases, as well as changes and logical manipulations of/to the variables. Using these data units, SNMP is actually a simple protocol for collecting and organizing information.
SNMP has evolved into three different versions:
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