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SNMP glossary

Simple Network Management Protocol (SNMP) uses specific terms and phrases to describe different aspects in the monitoring of network devices. The following table contains some of these items and the associated definitions:

Agent

A software service that resides and runs on a network device. This service monitors objects defined through one or more Management Information Base (MIB) files on the host system. The SNMP agent can send unsolicited trap messages to one or more Network Management Systems (NMSs) and respond to SNMP request messages with host device information.

Authentication protocol

A method of validating SNMPv3 messages.

Community

A string of characters that represents a group of SNMP-enabled network devices. Only Network Management Systems (NMSs) and SNMP agents that use the same SNMP community name can communicate with each other. Most SNMP agents support multiple community names, which allow the SNMP agents to receive SNMP requests from multiple NMSs.

The SNMPv1 and SNMPv2c standards support SNMP communities as a method of authorization.

SNMPv3 uses User-based Security Model (USM) for authentication and encryption. USM uses user and password for authentication, not a community name. While a community name is not required, supplying one allows communication with systems that use the earlier versions of SNMP.

Destination

The address of a Network Management System (NMS). The format of the address, such as IP address or fully-qualified domain name (FQDN), is dependent on the application in which you configure the destination.

An SNMP agent can send traps to one or more destinations.

Management Information Base (MIB)

A text file, in a specific format, that defines the information available in the host network device.

The format for MIB files is defined by Structure of Management Information, version 2 (SMIv2), which is included in RFC 2578.

Genesys has registered its own, unique SNMP MIB object:

interintelli(2793)

Objects in MIB files that are created by PureConnect are listed under the following object ID (OID):

.1.3.6.1.4.1.2793

Objects in MIB files from other sources use different OIDs. For example, MIBs such as aus.mib, HOST-RESOURCES-MIB.mib, and lmmib2.mib, which are common on host servers, are not created by Genesys and the objects contained within are not members under the .1.3.6.1.4.1.2793 OID.

Manager

See Network Management System.

Network device

A piece of computerized equipment that is connected to a network.

Examples of network devices that commonly use SNMP are servers, routers, switches, IP telephones, VoIP gateways, and printers.

Network Management System (NMS)

Also known as an SNMP manager, a network management system communicates with network devices through the SNMP protocol. An NMS can request status information for one or more variables defined in a MIB located on the network device. An NMS also receives unsolicited traps that are also defined in a MIB from SNMP network devices.

Object Identifier (OID)

Standard: section 3.1 in RFC1155. Every object in a MIB file is assigned an OID. It is through OIDs that SNMP agents and Network Management Systems (NMSs) communicate variable bindings, such as the current amount of free hard drive space.

Privacy protocol

A method of encrypting and decrypting SNMPv3 messages.

Protocol Data Units (PDU)

The format of an SNMP message. SNMP PDUs contain the following information:

  • IP header

  • UDP header

  • version

  • community

  • PDU-type

  • request-id

  • error-status

  • error-index

  • variable bindings

For information about the messages that can be sent or received through SNMP, see SNMP messages.

Request

A message that a Network Management System (NMS) sends to an SNMP agent. This message requests that the SNMP agent send status information about a specific variable to the NMS.

Traps

Unsolicted messages that an SNMP agent sends to a Network Management System (NMS) as specified in a destination address.

SNMP agents send trap messages when variables, as defined in Management Information Base (MIB) files on the network devices, meet a specific criterion, such as a lack of free hard drive space.

User

The identifier used in conjunction with a password to authenticate SNMPv3 messages.

Variable bindings

An object and one or more values as defined in a Management Information Base (MIB) file.

Each object has a unique object identifier (OID). Within an object, a MIB file can contain one or more values. The pairing of an object and the value is a variable binding.

For example, a MIB file may define an object for free storage space and includes the values of 20%, 10%, and 5%. The SNMP agent on the host network device sends a trap message when the free storage space of the network device reaches each of those defined thresholds.

Variable bindings do not apply only to trap messages. Some MIB files enable a Network Management System (NMS) to set values for an object through variable bindings as well.

Variables

One or more values assigned to an object in a Management Information Base (MIB) file.

Walk

A term that describes the process of a Network Management System (NMS) submitting a succession of GetNext SNMP requests to an SNMP agent on a network device. Usually, the succession of requests continues until the end of defined objects in a Management Information Base (MIB) file on the host network device.

Some operating systems contain an snmpwalk command that you can use to request data from an SNMP agent on a network device. Most NMS products also provide this functionality.