Configuration manual

SNMP Concepts
12-2 Configuring SNMP
2. Setting security access rights
3. Setting SNMP Management Information Base (MIB) view attributes
4. Setting target parameters to control the formatting of SNMP notification messages
5. Setting target addresses to control where SNMP notifications are sent
6. Setting SNMP notification parameters (filters)
7. Reviewing SNMP statistics
SNMP Concepts
Manager/Agent Model Components
SNMP provides a message format for communication between managers and agents, which use a
MIB and a relatively small set of commands to exchange information. The SNMP manager can be
part of a network management system, such as Enterasys NetSight
®
, while the agent and MIB
reside on the switch.
The SNMP agent acts upon requests from the manager to either collect data from the MIB or set
data into the MIB. A repository for information about device parameters and network data, the
MIB is organized in a tree structure in which individual variables are represented as leaves on the
branches. A unique object identifier (OID) distinguishes each variable in the MIB and is the means
by which the manager and agent specify which managed elements are changed.
An agent can send unsolicited notification messages (also known as traps or informs) alerting the
SNMP manager to a condition on the network. These conditions include such things as 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.
Message Functions
SNMP uses five basic message types (Get, Get Next, Get Response, Set, and Trap) to communicate
between the manager and the agent. The Get and Get Next messages allow the manager to request
information for a specific variable. The agent, upon receiving a Get or Get Next message, will issue
a Get Response message to the manager with either the information requested or an error
indication about why the request cannot be processed.
A Set message allows the manager to request a change to a specific variable. The agent then
responds with a Get Response message indicating the change has been made or an error
indication about why the change cannot be made.
A trap or inform message allows the agent to spontaneously inform the manager of an
“important” event in the network.
The SNMP manager and agent use information in the MIB to perform the operations described in
Table 12-1.
Table 12-1 SNMP Message Functions
Operation Function
get-request Retrieves a value from a specific variable.
get-next-request Retrieves a value from a variable within a table.
1
get-bulk-request
2
Retrieves large blocks of data, such as multiple rows in a table, that would otherwise
require the transmission of many small blocks of data.