Message Functions

SNMP uses five basic message types (Get, Get Next, Get Response, Set, and Trap) to communicate between the manager and the agent. The Get and Get Next messages allow the manager to request information for a specific variable. The agent, upon receiving a Get or Get Next message, will issue a Get Response message to the manager with either the information requested or an error indication about why the request cannot be processed.

A Set message allows the manager to request a change to a specific variable. The agent then responds with a Get Response message indicating the change has been made or an error indication about why the change cannot be made.

A trap or inform message allows the agent to spontaneously inform the manager of an “important” event in the network.

The SNMP manager and agent use information in the MIB to perform the operations described in The following table.

SNMP Message Functions

Operation	Function
get-request	Retrieves a value from a specific variable.
get-next-request	Retrieves a value from a variable within a table. 1
get-bulk-request 2	Retrieves large blocks of data, such as multiple rows in a table, that would otherwise require the transmission of many small blocks of data.
get-response	Replies to a get-request, get-next-request, and set-request sent by a management station.
set-request	Stores a value in a specific variable.
trap | inform 3	Unsolicited message sent by an SNMP agent to an SNMP manager when an event has occurred.