Managing Devices Using SNMP

Some network devices, services and applications can be controlled using SNMP. A set of available operations and methods of their invocation varies for different types of devices/services/applications.

Examples of Control Operations

There are two kinds of control operations that can be performed via SNMP: configuration alteration and direct action execution.

Changing Configuration

Changeable configuration settings for a managed SNMP device/service/application are exposed as writable variables (OIDs).

One of the simplest examples of configuring via SNMP is setting a "standard" value, e.g. one of described in RFC 1213. Say, to alter device description you can set value of sysDescr (1.3.6.1.2.1.1.1) to the desired string value.

Configuration changes can involve much more sophisticated procedures including related series of changes, table row creations, etc.

Action Execution

There are some actions that can be performed depending on concrete types of managed items. All those actions are still performed as SNMP Set operations for certain OIDs.

For example, to reload a Cisco switch you can write value 2 (representing reset operation) to a sysReset (1.3.6.1.4.1.9.2.9.9) variable.

How to Invoke Operations

Since all controlling operations in SNMP are actually alterations of variables (OIDs), to perform a control action a manager should set value of particular SNMP variable exposed by a managed device. The variables should be described in MIB files for the item. Refer to the documentation of device/service/application you want to control.

To write new value of a particular SNMP variable to the device you can follow the standard procedure:

  • Double-click the device item in the System Tree. The Device Configuration window should appear.
  • Select the variable you want to modify at an appropriate MIB tab. Alternatively you can disable tabbed layout and find the variable in plain list of all available variables.
  • Set the desired new value and save properties. This will start synchronization process which will write the value to the device.

    • Be careful changing parameters of real devices! Ensure you don't modify a parameter that is critical to the state of the system.

    You can automate the repetitious controlling operations using standard Iotellect Network Manager tools, e.g. widgets, scripts, alerts (their Automatic Correction Actions) etc.

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