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Chapter23 Configuring SNMP
Understanding SNMP
A community string can have one of these attributes:
•Read-only (RO)—Gives read access to authorized management stations to all objects in the MIB
except the community strings, but does not allow write access
•Read-write (RW)—Gives read and write access to authorized management stations to all objects in
the MIB, but does not allow access to the community strings
•Read-write-all—Gives read and write access to authorized management stations to all objects in the
MIB, including the community strings
Note When a cluster is created, the command switch manages the exchange of messages among member
switches and the SNMP application. The Cluster Management software appends the member switch
number (@esN, where N is the switch number) to the first configured RW and RO community strings on
the command switch and propagates them to the member sw itches. F or m ore info rmatio n, see Chapter5,
“Clustering Switches.”
Using SNMP to Access MIB Variables
An example of an NMS is the CiscoWorks network management software. CiscoWorks 2000 software
uses the switch MIB variables to set device variables and to poll devices on the network for specific
information. The results of a poll can appear as a graph and be analyzed to troubleshoot internetworking
problems, increase network performance, verify the configuration of devices, m onitor traffic loads, and
more.
As shown in Figure 23-1, the SNMP agent gathers data from the MIB. The agent can send traps, or
notification of certain events, to the SNMP manager, which receives and processes the traps. Traps alert
the SNMP manager to a condition on the network, such as imp rop er us er a uthe nti cati on, resta rts , l ink
status (up or down), MAC address tracking, and so forth. The SNMP agent also responds to MI B-related
queries sent by the SNMP manager in get-request, get-next-request, and set-request format.
Figure23-1 SNMP Network
For information on supported MIBs and how to access them, see Appendix A, “Supported MIBs.”
SNMP Notifications
SNMP allows the switch to send notifications to SNMP managers when particular events occur. SNMP
notifications can be sent as traps or inform requests. In command syntax, unless ther e is an option in the
command to select either traps or informs, the keyword traps refers to either traps or informs, or both.
Use the snmp-server host command to specify whether to send SNMP notifications as traps or informs.
Get-request, Get-next-request,
Get-bulk, Set-request Network device
Get-response, traps
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SNMP Manager
NMS
MIB
SNMP Agent