What Is MIB?

The MIB, or Management Information Base, is an ASCII text file that describes Simple Network Management Protocol (SNMP) elements as a list of data objects. Think of it as a dictionary of the SNMP language - every managed object referred to in an SNMP message must be listed in the MIB.

What does the MIB do?

The fundamental purpose of the MIB is to translate numerical strings into human-readable text. When an SNMP device sends a message or "trap," it identifies each data object in the message with a number string called an object identifier, or OID. (OIDs are defined more fully later in this paper.)

The MIB provides a text label called for each OID. Your SNMP manager uses the MIB as a codebook for translating the OID numbers into a human-readable display.

Why do I need the MIB?

Your SNMP manager needs it in order to process messages from your devices. Without the MIB, the message is just a meaningless string of numbers.

How do I get the MIB into my SNMP manager?

Your SNMP manager imports it by compiling the raw ASCII text of the file into binary that the SNMP management system can understand.

Why is the MIB important?

Because as far as SNMP managers and agents are concerned, if a component of a network device isn't defined in the MIB, it doesn't exist.

For example, let's say you have an SNMP RTU (Remote Telemetry Unit) with a built-in temperature sensor. You think you'll get temperature alarms from this device - but you never do, no matter how hot it gets. Why not? You read the RTU's MIB file and find out that it only lists discrete points, and not the temperature sensor. Since the sensor isn't defined in the MIB, the RTU can't send traps with temperature data.

Why do I need to understand the MIB?

As you can see, the MIB is your best guide to the real capabilities of an SNMP device. Just looking at the physical components of a device won't tell you what kind of traps you can get from it. You might think it's strange that a manufacturer would add a component to a device and not describe it in the MIB. But the fact is, a lot of devices have sketchy MIBs that don't fully support all their functions.

When you're planning your SNMP monitoring, you need to be able to read MIBs so you can have a realistic idea of what capabilities you have. When you're evaluating new SNMP equipment, examine its MIB file carefully before you purchase.

What Features Do I Need in an SNMP RTU (Remote Telemetry Unit)?

Here are 5 essential features that your SNMP RTU (Remote Telemetry Unit) must have:

1. Discrete alarm inputs (also called digital inputs or contact closures): These are typically used to monitor equipment failures, intrusion alarms, beacons, and flood and fire detectors.
2. Analog alarm inputs: Analog alarms measure continuously variable levels of voltage or current. Analog alarms monitor temperature, humidity and pressure, all of which can critically affect equipment performance.
3. Ping alarms: An RTU (Remote Telemetry Unit) that supports ping alarms will ping devices on your network at regular intervals. If a device fails to respond, the RTU (Remote Telemetry Unit) will send an alarm as an SNMP Trap.
4. Control relays: An RTU (Remote Telemetry Unit) with control relay outputs will let you operate remote site equipment directly from your NOC.
5. Terminal server function: Your RTU (Remote Telemetry Unit) can also serve as a terminal server to remote-site serial devices. Your devices connect to the RTU's serial ports, giving you immediate Telnet access via LAN from your NOC at any time.