Cisco MCS-7825-H3-IPC1 Service Guide - Page 150

SNMP Community Strings and Users Chapter 4 Simple Network Management Protocol SNMP Community Strings and Users Although SNMP community strings provide no security, the strings authenticate access to MIB objects and function as embedded passwords. You configure SNMP community strings for SNMP v1 and v2c only. SNMP v3 does not use community strings. It uses SNMP users that serve the same purpose as community strings but provide security because encryption or authentication is configured. No default community string or user exists. SNMP and Cisco MIBs You can access the Cisco MIB variables by using SNMP which facilitates the exchange of management information between network devices. The SNMP system comprises three parts: SNMP manager, SNMP agent, and MIB. Instead of defining a large set of commands, SNMP places all operations in a get-request, get-next-request, get-bulk-request, and set-request format. For example, an SNMP manager can get a value from an SNMP agent or store a value in that SNMP agent. The SNMP manager can comprise part of a network management system (NMS), and the SNMP agent can reside on a networking device such as a router. You can compile the Cisco MIB with your network management software. If SNMP is configured on a router, the SNMP agent can respond to MIB-related queries that are being sent by the NMS. The NMS uses the Cisco MIB variables to set device variables and to poll devices on the internetwork for specific information. The results of a poll can get graphed and analyzed to help you troubleshoot internetwork problems, increase network performance, verify the configuration of devices, monitor traffic loads, and more. The SNMP agent gathers data from the MIB, which provides the repository for information about device parameters and network data. The SNMP agent also can send traps (notifications) of certain events, to the SNMP manager. The Cisco host //ftp.cisco.com makes available the Cisco trap file, "mib.traps," which documents the format of Cisco traps. The SNMP manager uses information in the MIB to perform the operations as described: Operation get-request get-next-request get-response get-bulk-request set-request traps Description Retrieve a value from a specific variable. Retrieve the value following the named variable. Often used to retrieve variables from within a table. 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 the MIB. The reply to a get-request, get-next-request, get-bulk-request, and set-request sent by an NMS. Similar to get-next-request, but fills the get-response with up to max-repetition number of get-next interactions. Store a value in a specific variable. An unsolicited message sent by an SNMP agent to an SNMP manager indicating that some event has occurred. Cisco Unified Communications Manager Managed Services Guide 4-4 OL-22523-01