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.
SNMP Manager Functions
The SNMP manager uses information in the MIB to perform the operations described in the following table:
Table 47: SNMP Operations
DescriptionOperation
Retrieves a value from a specific variable.get-request
Retrieves a value from a variable within a table.
3
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
4
Replies to a get-request, get-next-request, and set-request sent by an NMS.get-response
Stores a value in a specific variable.set-request
An unsolicited message sent by an SNMP agent to an SNMP manager when some event
has occurred.
trap
3
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.
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
448
Restrictions for SNMP
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