SNMP has become the de facto standard for network management. SNMP is a simple solution that requires little code to implement, which enables vendors to easily build SNMP agents for their products. In addition, SNMP is often the foundation of the network management architecture. SNMP defines how management information is exchanged between network management applications and management agents. Figure 3-26 shows the terms used in SNMP; they are described as follows:

■ Manager: The manager, a network management application in an NMS, periodically polls the SNMP agents that reside on managed devices for the data, thereby enabling information to be displayed using a GUI on the NMS. A disadvantage of periodic SNMP polling is the possible delay between when an event occurs and when it is collected by the NMS; there is a trade-off between polling frequency and bandwidth usage.

■ Protocol: SNMP is a protocol for message exchange. It uses the User Datagram Protocol (UDP) transport mechanism to send and retrieve management information, such as MIB variables.

■ Managed device: A device (such as a router) managed by the manager.

■ Management agents: SNMP management agents reside on managed devices to collect and store a range of information about the device and its operation, respond to the manager's requests, and generate traps to inform the manager about certain events. SNMP traps are sent by management agents to the NMS when certain events occur. Trap notifications could result in substantial network and agent resource savings by eliminating the need for some SNMP polling requests.

■ MIB: The management agent collects data and stores it locally in the MIB, a database of objects about the device. Community strings, which are similar to passwords, control access to the MIB. To access or set MIB variables, the user must specify the appropriate read or write community string; otherwise, access is denied.

Figure 3-26 NMP Is a Protocol for Management Information Exchange a


SNMP Protocol for Message Exchange

Managed Device

Managed Device

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