Cisco MCS-7825-H3-IPC1 Service Guide - Page 149

Chapter 4 Simple Network Management Protocol SNMP and Cisco Unified CM Basics SNMPv3 prevents packets from being exposed on the network. Instead of using community strings like SNMP v1 and v2, SNMP v3 uses SNMP users, as described in the "SNMP Community Strings and Users" section on page 4-4. SNMP and Cisco Unified CM Basics A network that uses SNMP requires three key components-managed devices, agents, and network management software (NMS). • Managed devices-Devices that contain SNMP agents and reside on a network. Managed devices collect and store information and make it available by using SNMP. - The first node in the Cisco Unified CM cluster acts as the managed device. In Cisco Unified CMBE, the server on which Cisco Unified CM is installed acts as the managed device. • Agents-Software modules that contain local knowledge of management information and translates it into a form that is compatible with SNMP. - Cisco Unified CM uses a master agent and subagent components to support SNMP. The master agent acts as the agent protocol engine and performs the authentication, authorization, access control, and privacy functions that relate to SNMP requests. It contains a few Management Information Base (MIB) variables. The master agent also connects and disconnects subagents after the subagent completes necessary tasks. - Cisco Unified CM uses a subagent to interact with the local Cisco Unified CM only. The Cisco Unified CM subagents send trap and information messages to the SNMP Master Agent, and the SNMP Master Agent communicates with the SNMP trap receiver (notification destination). • NMS-SNMP management application that runs on a PC and provides the bulk of the processing and memory resources that are required for network management. It executes applications that monitor and control managed devices. Cisco Unified Communications Manager works with the following NMS: - CiscoWorks2000 - HP OpenView - Third-party applications that support SNMP and Cisco Unified Communications Manager SNMP interfaces SNMP Basic Commands Managed devices get monitored and controlled by using four basic SNMP commands: read, write, trap, and traversal operations. • NMS uses the read command to monitor managed devices. The NMS examines different variables that are maintained by managed devices. • NMS uses the write command to control managed devices. The NMS changes the values of variables stored within managed devices. • Managed devices use the trap command to asynchronously report events to the NMS. When certain types of events occur, a managed device sends a trap to the NMS. • NMS uses traversal operations to determine which variables a managed device supports and to sequentially gather information in variable tables, such as a routing table. OL-22523-01 Cisco Unified Communications Manager Managed Services Guide 4-3