SNMP OID: Introduction for Industry Professionals

"OID" stands for Object IDentifier.

You can think of an OID as an address used in SNMP messages to identify devices and their statuses - acting both as the "What is it?" as well as the "Where did it come from?" Want to know the temperature reading coming from a sensor at your mountaintop remote facility? There's an OID for that.

SNMP Object Identifiers (OIDs) point to network objects stored in a database called the Management Information Base, often referred to as the "MIB". A MIB holds the structure of the network alarms being monitored (like a map of the "city"), and it uses the OIDs to keep track of the individual components (like the address to a house or other location). In this example, an SNMP OID is like the address the fire truck would drive to if the fire alarm sounded. What if a fire broke out at your house, and you called the fire department with GPS coordinates (representing the Object ID or OID)? The fire department would have to look that up in its MIB to determine the correct street address. In telecom, SNMP OIDs describe specific locations in the network. The OID allows the MIB to translate the location of the event into a status description for your network technicians.

Learn more about MIBs

How do you read an OID?

While it may look daunting, the OID follows a simple structure, with each "dot" segment identifying part of a network element.

• The further right in the OID string you go, the more specific you get.


• The first handful of numbers in gray don't usually change, similar to how home addresses are all (usually) in this solar system and on this planet - they're the givens of the OID world.


• The red '2682' in the middle is the start of the unique part of the string and represents the manufacturer of the device using the OID, in this case: DPS.


• The rest of the numbers following it in blue are for defining a specific object, in this case it's the state of an alarm in a DPS RTU.

An SNMP Manager (ex. T/Mon) translates these SNMP OIDs into a value that is then assigned readable labels in the Management Information Base (MIB). This allows the SNMP manager to produce messages that can be read by people.

When the SNMP Manager requests the value ("state") of any object it is monitoring, it sends a message with that object's OID to its Management Information Base. The MIB will decode the address and attach a text description to it. This allows the SNMP Manager to present the value of the alarm condition with the identifying description of the labeled alarm.

Now you've completely read through this OID

Now you know that you're dealing with the state of discrete alarm point #1 on an RTU manufactured by DPS Telecom. Not bad for a string of numbers, huh?

Who decides on the structure of SNMP OIDs?

OIDs are defined in the SNMP MIB file, a kind of "codebook" for SNMP. The manufacturer (DPS Telecom in this example) spells out the second half of the OID for their own devices by supplying a MIB file to their users. The first half is established by a standard referenced "RFC" MIB used worldwide.

Let's consider the OID from a slightly different angle now...

To monitor network alarms, you must know your alarm points. Your apartment or house address indicates a specific location by country, state, city, zip code, street, and house number. SNMP has Object Identifiers (OIDs) that define each thing for the manager and agents.

SNMP Object Identifiers (OIDs) point to network objects stored in a database called the Management Information Base, often referred to as the "MIB". A MIB holds the structure of the network alarms being monitored (like a map of the "city"), and it uses the OIDs to keep track of the individual components (like the address to a house or other location). In this example, an SNMP OID is like the address the fire truck would drive to if the fire alarm sounded. What if a fire broke out at your house, and you called the fire department with GPS coordinates (representing the Object ID or OID)? The fire department would have to look that up in its MIB to determine the correct street address.

In telecom, SNMP OIDs describe specific locations in the network. The OID allows the MIB to translate the location of the event into a status description for your network technicians.

This message is captured by the SNMP Manager which again uses the Management Information Base to tie the OID sensor message that was reported by the "driveway sensor" (a simple "No" response) back into the human readable 123 Main St. which is displayed.

If an object does not have an OID listed within an MIB, the SNMP Manager cannot identify it. Even if that object has a sensor and can transmit data, he SNMP Manager is blind without the MIB. For a condition or device to be monitored, it must have a corresponding MIB definition.

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Here at DPS, we will occasionally have clients that require specific MIBs for their applications. One client, James, needed to be able to identify all of the printers on his LAN via SNMP by asking every device for its OID at user-defined time intervals. He needed to email any reporting events to the SNMP monitor, and he had to do that without busting his budget.

Another client had a need to send certain SET commands to remote units at some microwave sites. The units were not capable of sending those commands. Our solution had custom OIDs that were configured with variable bindings to accept SNMP Traps. This allowed monitoring and control of the remote microwave sites with the ability to toggle up to 40 discrete relays in the system. This solution saved them money and down time and increased the use of existing equipment for the customer.

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Finally, remember that the first several pieces of each OID are almost always the same. These upper location levels are defined by a series of standard reference within the MIB. These series are called RFCs, or Requests for Comments. The RFCs that define SNMP OIDs are part of a larger group of RFC documents that define the Internet as a whole. Individual vendors create their own MIBs that only include the OIDs for their device.