27-3
Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 27 Configuring SNMP
Understanding SNMP
You must configure the SNMP agent to use the SNMP version supported by the management station.
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 SNMP manager uses information in the MIB to perform the operations described in
Table 27-1
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
authNoPriv
MD5 or SHA
No
Provides authentication based on the HMAC-MD5
or HMAC-SHA algorithms.
SNMPv3
authPriv
(requires the
cryptographic software
image)
MD5 or SHA
DES
Provides authentication based on the HMAC-MD5
or HMAC-SHA algorithms.
Provides DES 56-bit encryption in addition to
authentication based on the CBC-DES (DES-56)
standard.
Table 27-2
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-request
2
2.
The get-bulk command only works with SNMPv2 or later.
Retrieves large blocks of data, such as multiple rows in a table, that would
otherwise require the transmission of many small blocks of data.
get-response
Replies to a get-request, get-next-request, and set-request sent by an NMS.
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.