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Restrictions for SNMP
Version Restrictions
•
SNMPv1 does not support informs.
Information About SNMP
SNMP Overview
SNMP is an application-layer protocol that provides a message format for communication between managers
and agents. The SNMP system consists of an SNMP manager, an SNMP agent, and a management information
base (MIB). The SNMP manager can be part of a network management system (NMS) such as Cisco Prime
Infrastructure. The agent and MIB reside on the switch. To configure SNMP on the switch, you define the
relationship between the manager and the agent.
The SNMP agent contains MIB variables whose values the SNMP manager can request or change. A manager
can get a value from an agent or store a value into the agent. The agent gathers data from the MIB, the repository
for information about device parameters and network data. The agent can also respond to a manager's requests
to get or set data.
An agent can send unsolicited traps to the manager. Traps are messages alerting the SNMP manager to a
condition on the network. Traps can mean improper user authentication, restarts, link status (up or down),
MAC address tracking, closing of a TCP connection, loss of connection to a neighbor, or other significant
events.
The active switch handles the SNMP requests and traps for the whole switch stack. The active switch
transparently manages any requests or traps that are related to all stack members. When a new active switch
is elected, the new active switch continues to handle SNMP requests and traps as configured on the previous
active switch, assuming that IP connectivity to the SNMP management stations is still in place after the new
active switch has taken control.
SNMP Manager Functions
The SNMP manager uses information in the MIB to perform the operations described in the following table:
Table 8: SNMP Operations
DescriptionOperation
Retrieves a value from a specific variable.get-request
Retrieves a value from a variable within a table.
2
get-next-request
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-bulk-request
3
Replies to a get-request, get-next-request, and set-request sent by an NMS.get-response
Catalyst 2960-X Switch Network Management Configuration Guide, Cisco IOS Release 15.0(2)EX
46 OL-29044-01
Configuring Simple Network Management Protocol
Restrictions for SNMP