There are several ways that the SNMP manager and the agent communicate. The manager can:

Retrieve a value (get) The SNMP manager requests information from the agent, such as the number of users logged on to the agent device or the status of a critical process on that device. The agent gets the value of the requested Management Information Base (MIB) variable and sends the value back to the manager.

Retrieve the value immediately after the variable you name (get-next) The SNMP manager retrieves different instances of MIB variables. The SNMP manager takes the variable you name and then uses a sequential search to find the desired variable.

Retrieve a number of values (get-bulk) The SNMP manager retrieves the specified number of instances of the requested MIB variable. This minimizes the number of protocol exchanges required to retrieve a large amount of data.

Change a configuration on the agent (set) The SNMP manager requests the agent to change the value of the MIB variable. For example, you can run a script or an application on a remote device with a set action.

Receive an unsolicited message (notification) The SNMP manager receives an unsolicited message from an agent at any time if a significant, predetermined event takes place on that agent. When a notification condition occurs, the SNMP agent sends an SNMP notification to the device specified as the trap receiver or trap host. The SNMP Administrator configures the trap host, usually the SNMP management station, to perform the action needed when a trap is detected.