devices through the SNMP agent. The SNMP manager
offers a monitoring and management interface to
network and system administrators. The SNMP
components and their interactions are illustrated in
Figure 18-5.
Figure 18-5 SNMP Components
The SNMP agent listens on UDP port 161 for requests
from the SNMP manager. SNMP also supports
notifications, which are SNMP messages that are
generated on the managed device when significant
events take place. Through notifications, the SNMP
agent notifies the SNMP manager about these critical
events. The NMS listens for these notifications on UDP
port 162. SNMP data structures that facilitate the
exchange of information between the SNMP agent and
the NMS are organized as a list of data objects called a
Management Information Base (MIB). A MIB can be
thought of as a map of all components of a device that