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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 24 Configuring SNMP
Unders tanding SNMP

SNMP Community Strings

SNMP comm unity stri ngs authent icate acc ess to MIB object s and functio n as embedde d passwords. In
order for the NMS to access th e switch, the community string def initions on the NMS must match at least
one of the thr ee com mu nity st rin g definitions on the sw itc h.
A com mun ity st ring c an h ave one of t hese at tribute s:
•Read-only (RO)—Gives read access to authorized management stations to all objects in the MIB
except th e co mmuni ty stri ngs, but doe s not al low write ac ces s
•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—Giv es read and write access to authorized man agement statio ns to all objects in the
MIB, inc ludi ng the com mu nit y s tri ngs
Note Whe n a cluster is creat ed, the comm and swit ch manage s the exchange of me ssages amon g member
switches and the SNMP application. The Cluster Management software appends the member switch
number (@esN, wher e N is the switch numbe r) to the first conf igured RW and RO community strin gs on
the co mmand swit ch a nd propag ates them to th e memb er switch es. F or mor e infor mation, see Chapter 6,
“Clustering Switches.”

Using SNMP to Access MIB Variables

An examp le o f an N MS is th e Cisc oWorks net work m anag em ent sof twar e. C iscoWorks 200 0 soft ware
uses the switch MIB variables to set device variables and to poll devices on the network for specific
inform ati on. T he res ul ts of a pol l c an b e displ aye d as a gra ph and a naly zed to t roub lesho ot
interne tworking pro blems , increase network perf orman ce, verify the con figuration of devices, monitor
traffic load s, and mor e.
As shown in Figure 24-1, 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 co nditi on on the networ k such as impr oper user au then ticatio n, restar ts, lin k
status (up or down), MAC address tracking, and so forth. The SNMP agent also responds to MIB-related
queries sent by the SNMP manage r in get-request, get-next-request, an d set-request forma t.
Figure 24-1 SNMP Netw ork
For informati on on supporte d MIBs and how to access them, s ee Appendix A, “Sup ported MIBs. ”
Get-request, Get-next-request,
Get-bulk, Set-request Network device
Get-response, traps
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SNMP Manager
NMS
MIB
SNMP Agent