Snmp; Overview Of Snmp - GE PACSystems RX3i User Manual

Chapter 7. Network Management
7.1

SNMP

The built-in SNMP (Simple Network Management Protocol) Server/Agent function on the PROFINET Controller
can be used by a third-party SNMP Client or Network Management Station to access network data.
7.1.1

Overview of SNMP

SNMP is a UDP-based network protocol that facilitates the exchange of management information between
network devices. An SNMP-managed network consists of three key components: managed devices, agents, and
network management systems (NMS).
A managed device is a network node that contains an SNMP agent and that resides on a managed network.
Managed devices exchange management information with NMSs via their local agent.
An agent is a network management software module that resides on a managed device. An agent maintains a
collection of management information that it provides in an SNMP-compatible format upon request to NMSs.
An NMS executes applications that monitor and control managed devices.
The collections of management information maintained by agents and managed devices are generally referred
to as Management Information Bases (MIBs). A MIB is a collection of information organized into a hierarchical
structure where related items are grouped together in "groups." MIBs are used to organize and standardize the
management information on agents and can be accessed via commands provided within the SNMP protocol.
The SNMP protocol is currently defined by five protocol specifications: SNMPv1, SNMPv2, SNMPv2c, SNMPv2u,
and SNMPv3.
NMSs use four basic classes of SNMP commands to retrieve and alter data on managed devices
•
The read (GET) command is used by an NMS to monitor managed devices through examination of the
values of different variables maintained within the managed devices' MIBs.
•
The write (SET) command is used by an NMS to control devices through modification of the values
maintained by the managed devices within their MIBs.
•
The trap (TRAP, INFORM) command is used by an NMS to get asynchronous notifications when certain
events occur on managed devices. In SNMP Version 2, traps are not set via the protocol but are defined at
the managed device by local action.
•
Traversal operations (GETNEXT and GETBULK) are used by an NMS to determine which variables a
managed device supports and to sequentially gather information from the MIBs.
SNMP is a well-defined protocol; additional information is available in the literature and on the World Wide
Web.
142 PACSystems* RX3i & RSTi-EP PROFINET IO-Controller User Manual GFK-2571N