SNMP Trap Probes

type = "custom-snmp-trap"

A trap is an unsolicited packet sent from a device to Intermapper (or another SNMP management console). Traps generally contain one or more data values that provide information about the state of the device.

When a trap arrives, Intermapper determines which device on the enabled maps should receive information from the trap. Intermapper examines the Agent Address (for relayed traps) or the Source IP address, and passes a copy of the trap packet to each device on the maps where the IP addresses match. For example, if a device with the IP address is on two maps, or is present twice on the same map, each device receives a copy of the trap.

Intermapper then parses out the values from the trap and assigns them to trap variables for the remainder of the probe. Intermapper re-evaluates the expressions in the probe and sets the device status appropriately. If a trap variable is not set by an incoming trap, expressions containing that variable are not evaluated. See The <snmp-device-variables> Section for Traps for more information on defining trap variables.

Finally, as a result of receiving the trap, Intermapper re-polls the device that sent the trap. This guarantees that Intermapper has the most up-to-date information about the state of the device. If another trap arrives before the final response of this new poll has returned, Intermapper completes the current poll and initiates another round of polling to obtain the new state.

For information on how to retrieve and display trap contents, see Example Trap Probe.