Cisco Dial NMS Implementation Manual page 15

Figure 1 illustrates the relationship between the managed devices, the agent, and the NMS.
Agent
Management
Database
There are three basic SNMP message types:
Get—NMS-initiated requests used by an NMS to monitor managed devices. The NMS examines
different variables that are maintained by managed devices.
Set—NMS-initiated commands used by an NMS to control managed devices. The NMS changes
the values of variables stored within managed devices.
Trap—Agent-initiated messages sent from a managed device, which reports events to the NMS.
The Cisco IOS generates SNMP traps for many distinct network conditions. Through SNMP traps,
the Network Operations Center (NOC) is notified of network events, such as:
`
Link up/down changes
`
Configuration changes
`
Temperature thresholds
`
CPU overloads
For a list of Cisco-supported SNMP traps, go to
http://www.cisco.com/public/mibs/traps/
Management
Entity
NMS
Agent
Management
Database
Managed Devices
Agent
Management
Database