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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 24 Configuring SNMP Understanding SNMP
You must co nfigure the SNMP a gent to use the SNMP ver sion supporte d by the manage ment stati on.
Because an agent can communicate with multiple managers, you can configure the software to support
communications with one management station using the SNMPv1 protocol, one using the SNMPv2C
protocol and another using SNMPv3.

SNMP Manager Functions

The SN MP mana ger use s inf or ma tion i n the MIB to pe rfo rm t he o pe rat ions des cr ibed in Table 24-2.

SNMP Agent Functions

The SNMP agent responds to SNMP m anager requests as follows:
•Get a MIB variable—The SNMP agen t begins this function in response to a requ est f rom the NM S.
The agen t ret rieves the value o f the re qu este d MI B variabl e a nd resp onds t o the NMS w ith t ha t
value.
•Set a MI B v ariable —The SNMP agent begins this function in response to a message from the NMS.
The SN MP ag ent c hange s the valu e of the MIB variabl e to t he value req ues ted by the N MS.
The SNMP agent also sends unsolicited trap messages to notify an NMS that a significant event has
occurred on the agent. Examples of tra p conditions include, b ut are not limited to, whe n a port or module
goes up or down, when spanning- tree topol ogy change s occur, and when authe nticati on failures occur.
Table 24-1 SNMP Security Models and Levels
Model Level Authentication Encryption Result
SNMPv1 noAuthNoPriv Community string No Uses a community string match for authentication.
SNMPv2C noAuthNoPriv Community string No Uses a community string match for authentication.
SNMPv3 noAuthNoPriv Username No Uses a username match for authentication.
SNMPv3 authNoPri v MD5 or SHA No Pro vides authenticatio n based on the HMA C-M D5
or HMAC-SHA algorithms.
Table 24-2 SNMP Operations
Operation Description
get-request Retrieves a value from a specific variable.
get-next-request Retrieves a value from a variable within a table.1
1. With this operation, an SNMP manager does not need to know the exact variable name. A sequential search is performed to
find the needed variable from within a table.
get-bulk-request2
2. The get-bulk command only works with SNMPv2 or later.
Retrieves large blocks of data, such a s multipl e rows in a table, that would
otherwi se r equi re t he tran smissi on of m a ny small bloc ks of da ta.
get-re spon se Replies to a get -requ est, ge t-n ext-reque st, an d set-r eque st se nt by a n N MS.
set-request Stores a value in a specific variable.
trap An unsolicited message sent by an SNMP agent to an SNMP manager when some
event has occurred.