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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter18 Configuring SNMP
Understanding SNMP
SNMP Versions
This software release supports these SNMP versions:
•SNMPv1—The Simple Network Management Protocol, a Full Internet Standard, defined in
RFC 1157.
•SNMPv2C, which has these features:
–
SNMPv2—Version 2 of the Simple Network Management Protocol, a Draft Internet Standard,
defined in RFCs 1902 through 1907.
–
SNMPv2C—The Community-based Administrative Framework for SNMPv2, an Experimental
Internet Protocol defined in RFC 1901.
SNMPv2C replaces the Party-based Administrative and Security Framework of SNMPv2Classic with
the Community-based Administrative Framework of SNMPv2C while retaining the bulk retrieval and
improved error handling of SNMPv2Classic.
Both SNMPv1 and SNMPv2C use a community-based form of security. The community of managers
able to access the agent’s MIB is defined by an IP address access control list and password.
SNMPv2C includes a bulk retrieval mechanism and more detailed error message reporting to
management stations. The bulk retrieval mechanism retrieves tables and large quantities of information,
minimizing the number of round-trips required. The SNMPv2C i mp roved e rro r-handlin g in cl udes
expanded error codes that distinguish different kinds of error con dit ions; th ese con di tions ar e repor ted
through a single error code in SNMPv1. Error return codes now re por t the err or type .
You must configure the SNMP agent to use the version of SNMP supported by the management station.
An agent can communicate with multiple managers; for this reason, you can configure the software to
support communications with one management station using the SNMPv1 protocol and another using
the SNMPv2 protocol.
SNMP Manager Functions
The SNMP manager uses information in the MIB to perform the o pera tio ns des cr ibed in Table18-1.
Table18-1 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.
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.