Cisco WS-C4003 Software Guide - Page 306
SNMP ifindex Persistence Feature, Understanding How SNMPv1 and SNMPv2c Work
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Understanding How SNMPv1 and SNMPv2c Work Chapter 23 Configuring SNMP • A group determines the list of notifications its users can receive. • A group also defines the security model and security level for its users. SNMP ifindex Persistence Feature The SNMP ifIndex persistence feature is always enabled. With the ifIndex persistence feature, the ifIndex value of the port and VLAN is always retained and used after the following occurrences: • Switch reboot • High-availability switchover • Software upgrade • Module reset • Module removal and insertion of the same type of module For Fast EtherChannel and Gigabit EtherChannel interfaces, the ifIndex value is only retained and used after a high-availability switchover. 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 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 NMSs specified as the trap receivers, 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 23-4 Software Configuration Guide-Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4 78-12647-02