Cisco WS-C2960S-24PD-L Software Guide - Page 94

SNMP Network Management Platforms Chapter 4 General Switch Administration Using SNMP to Access MIB Variables The switch MIB variables are accessible through SNMP, an application-layer protocol facilitating the exchange of management information between network devices. The SNMP system consists of three parts: • The SNMP manager, which resides on the network management system (NMS) • The SNMP agent, which resides on the switch • The MIBs that reside on the switch but that can be compiled with your network management software An example of an NMS is the CiscoWorks network management software. CiscoWorks2000 software uses the switch MIB variables to set device variables and to poll devices on the network for specific information. The results of a poll can be displayed as a graph and analyzed to troubleshoot internetworking problems, increase network performance, verify the configuration of devices, monitor traffic loads, and more. As shown in Figure 4-1, the SNMP agent gathers data from the MIB, which is the repository for information about device parameters and network data. The agent can send traps, or notification of certain events, to the SNMP manager, which receives and processes the traps. Traps are messages alerting the SNMP manager to a condition on the network such as improper user authentication, restarts, link status (up or down), and so forth. In addition, the SNMP agent responds to MIB-related queries sent by the SNMP manager in get-request, get-next-request, and set-request format. The SNMP manager uses information in the MIB to perform the operations described in Table 4-1. Figure 4-1 SNMP Network NMS Get-request, Get-next-request, Get-bulk, Set-request Network device S1203a Get-response, traps SNMP Manager MIB SNMP Agent Table 4-1 SNMP Operations Operation Description get-request get-next-request get-bulk-request2 Retrieves a value from a specific variable. Retrieves a value from a variable within a table.1 Retrieves large blocks of data, such as multiple rows in a table, which 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 indicating that some event has occurred. 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. 2. The get-bulk command only works with SNMP version 2. Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide 4-6 78-6511-08