SNMP is an application-layer protocol that provides a message format for communication between managers and agents.

The SNMP system consists of an SNMP manager, an SNMP agent, and a MIB.

The SNMP manager can be part of a network management system (NMS). The agent and MIB reside on the switch/router etc.

The SNMP agent contains MIB variables whose values the SNMP manager can request or change. A manager can get a value from an agent or store a value into the agent. The agent gathers data from the MIB, the repository for information about device parameters and network data. The agent can also respond to a manager’s requests to get or set data.

An agent can send unsolicited traps to the manager. Traps are messages alerting the SNMP manager to a condition on the network. Traps can mean improper user authentication, restarts, link status (up or down), MAC address tracking, closing of a TCP connection, loss of connection to a neighbor, or other significant events.

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