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Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Software Configuration Guide—Release 8.2GLX
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Chapter 24 Configuring SNMP
Understanding How SNMPv1 and SNMPv2c Work
Understanding How SNMPv1 and SNMPv2c Work
The components of SNMPv1 and SNMPv2c network management fall into three categories:
•
Managed devices (such as a switch)
•
SNMP agents and MIBs, including Remote Monitoring (RMON) MIBs, which run on managed
devices
•
SNMP management applications, such as CiscoWorks2000, which communicate with agents to get
statistics and alerts from the managed devices
Note
An SNMP management application, together with the computer it runs on, is called a
network management system (NMS).
SNMP network management uses these SNMP agent functions:
•
Accessing a MIB variable—This function is initiated by the SNMP agent in response to a request
from the NMS. The agent retrieves the value of the requested MIB variable and responds to the NMS
with that value.
•
Setting a MIB variable—This function is also initiated by the SNMP agent in response to an NMS
message. The SNMP agent changes the MIB variable value to the value that is requested by the
NMS.
•
SNMP trap—This function is used to notify an NMS that a significant event has occurred at an
agent. When a trap condition occurs, the SNMP agent sends an SNMP trap message to any NMS
that is specified as a trap receiver under the following conditions:
–
When a port or module goes up or down
–
When temperature limitations are exceeded
–
When there are spanning tree topology changes
–
When there are authentication failures
–
When power supply errors occur
•
SNMP community strings—SNMP community strings authenticate access to MIB objects and
function as embedded passwords as follows:
–
Read-only—Gives only read access to all objects in the MIB except the community strings
–
Read-write—Gives read and write access to all objects in the MIB; does not allow access to
community strings
–
Read-write-all—Gives read and write access to all objects in MIB including community strings
Note
The community string definitions on your NMS must match at least one of the three community string
definitions on the switch.
Catalyst enterprise LAN switches are managed devices that support SNMP network management with
the following features:
•
SNMP traps (see the
“Configuring SNMPv1 and SNMPv2c from the CLI” section on page 24-9
)
•
RMON in the supervisor engine module software (see
Chapter 25, “Configuring RMON”
)
•
RMON and RMON2 on an external SwitchProbe device