Snmp

SNMP and its commands and describing MIB-1/MIB-2, including the hierarchical tree

As part of the configuration of a managed device, you can also identify whether it should be configured for read access, write access, or both. If configured for read access, an NMS like HP OpenView can gather information about the device. If configured for write access, an NMS can also configure the device using SNMP commands. The choice will depend upon whether you want to use the NMS strictly for gathering information or for configuration purposes also.

Get. The Get operation is used by an NMS to obtain a single piece of information from a managed device. For example, the NMS may be requesting the device’s configured name. “Get” is a read operation.

GetNext. The GetNext operation is issued by an NMS in order to obtain more than one piece of information from a managed device. For example, the NMS may wish to obtain both the name and system uptime of a particular device. In SNMPv1, when an NMS wants to obtain multiple pieces of information from a managed device, its only option is to issue Get and GetNext commands. “GetNext” is also a read operation.

Set. The Set command is used by an NMS to configure a managed device with a particular value. For example, maybe the NMS wants to configure or “set” a threshold on a managed device that tells it to alert the NMS if its CPU utilization hits 70% for a defined period of time. “Set” is a write operation.

Trap. A Trap operation is different that those described above, because it is initiated from a managed device. A trap message is used to alert an NMS to the fact that a threshold defined by the NMS (with the set command) has been reached, or that an error/event of some type has occurred. For example, a router may have been configured to set a trap message to an NMS when its average CPU utilization is over 70% for a period of one minute. Trap messages are said to be asynchronous, in that a managed device sends them without a request...