Cisco WS-C2980G-A Software Guide - Page 373

Chapter 24 Configuring SNMP Understanding How SNMPv1 and SNMPv2c Work Understanding How SNMPv1 and SNMPv2c Work The components of SNMPv1 and SNMPv2c network management fall into three categories: • Managed devices (such as a switch) • SNMP agents and MIBs, including Remote Monitoring (RMON) MIBs, which run on managed devices • SNMP management applications, such as CiscoWorks2000, which communicate with agents to get statistics and alerts from the managed devices Note An SNMP management application, together with the computer it runs on, is called a network management system (NMS). SNMP network management uses these SNMP agent functions: • Accessing a MIB variable-This function is initiated by the SNMP agent in response to a request from the NMS. The agent retrieves the value of the requested MIB variable and responds to the NMS with that value. • Setting a MIB variable-This function is also initiated by the SNMP agent in response to an NMS message. The SNMP agent changes the MIB variable value to the value that is requested by the NMS. • SNMP trap-This function is used to notify an NMS that a significant event has occurred at an agent. When a trap condition occurs, the SNMP agent sends an SNMP trap message to any NMS that is specified as a trap receiver, under the following conditions: - When a port or module goes up or down - When temperature limitations are exceeded - When there are spanning tree topology changes - When there are authentication failures - When power supply errors occur • SNMP community strings-SNMP community strings authenticate access to MIB objects and function as embedded passwords: - Read-only-Gives only read access to all objects in the MIB except the community strings - Read-write-Gives read and write access to all objects in the MIB; does not allow access to community strings - Read-write-all-Gives read and write access to all objects in MIB, including community strings Note The community string definitions on your NMS must match at least one of the three community string definitions on the switch. Catalyst enterprise LAN switches are managed devices that support SNMP network management with the following features: • SNMP traps (see the "Configuring SNMPv1 and SNMPv2c from the CLI" section on page 24-6) • RMON in the supervisor engine module software (see Chapter 25, "Configuring RMON") • RMON and RMON2 on an external SwitchProbe device 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 24-5