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4. SNMP NETWORK MANAGEMENT
The Simple Network Management Protocol (SNMP) is an application-layer protocol that facilitates
the exchange of management information between network devices. It is part of the TCP/IP
protocol suite. SNMP enables network administrators to manage network performance, find and
solve network problems, and plan for network growth.
SNMP consists of the following key components:
Managed device
is a network node that contains SNMP agent. Managed devices collect and
store management information and make this information available to NMS using SNMP.
Managed devices can be switches/Hub, etc.
MIB
(Management Information Base) defines the complete manageable entries of the managed
device. These MIB entries can be either read-only or read-write. For example, the System Version
is read-only variables. The Port State Enable or Disable is a read-write variable and a network
administrator can not only read but also set its value remotely.
SNMP Agent
is a management module resides in the managed device that responds to the
SNMP Manager request.
SNMP Manager/NMS
executes applications that monitor and control managed devices. NMS
provide the bulk of the processing and memory resources required for the complete network
management. SNMP Manager is often composed by desktop computer/work station and software
program such as HP OpenView. Totally, 4 types of operations are used between SNMP Agent &
Manager to change MIB information. These 4 operations all use the UDP/IP protocol to exchange
packets.
GET:
This command is used by an SNMP Manager to monitor managed devices. The SNMP
Manager examines different variables that are maintained by managed devices.
GET Next:
This command provides traversal operation and is used by the SNMP Manager to
sequentially gather information in variable tables, such as a routing table.
SET:
This command is used by an SNMP Manager to control managed devices. The NMS
changes the values of variables stored within managed devices.
Trap:
Trap is used by the managed device to report asynchronously a specified event to the
SNMP Manager. When certain types of events occur, a managed device will send a trap to alert
the SNMP Manager. The system built-in management module also supports SNMP management.
Users must install the MIB file before using the SNMP based network management system. The
MIB file is on a disc or diskette that accompanies the system. The file name extension is .mib,
which SNMP based compiler can read.
Please refer to the appropriate documentation for the instructions of installing the system private
MIB.
